THE USE OF PROTOTYPE COMPOUNDS TO STUDY NEUROTOXICITY:
A CASE STUDY OF THE ORGANOTINS
Deliverable Number 2595
Diane B. Miller
U.S. Environmental Protection Agency
Office of Health Research
Health Effects Research Laboratory
Neurotoxicology Division (MD-74B)
Research Triangle Park, NC 27711
September 30, 1990
This deliverable is an executive summary of a number of published experiments. The
publications are referenced in this summary and are contained in the Appendices in full
length and annotated form.
-------
THE USE OF PROTOTYPE COMPOUNDS TO STUDY NEUROTOXICITY:
A CASE STUDY OF THE ORGANOTINS
Deliverable Number 2595
Diane B. Miller
U.S. Environmental Protection Agency
Office of Health Research
Health Effects Research Laboratory
Neurotoxicology Division (MD-74B)
Research Triangle Park, NC 27711
September 30,1990
This deliverable is an executive summary of a number of published experiments. The
publications are referenced in this summary and are contained in the Appendices in full
length and annotated form.
-------
Executive Summary
The potential for a large number of chemicals to be neurotoxic poses a problem for
a number of the EPA program offices charged with regulating chemicals. Few of the
65,000 chemicals used in daily commerce have been assessed for neurotoxic potential but
of the chemicals that have been evaluated the Office of Technology Assessment (OTA)
estimates at least 25% are neurotoxic (OTA, 1984). Given the potential for many chemicals
to have neurotoxic actions there is a critical need for neurotoxicity risk assessment. The
Neurotoxicology Division (NTD) is the focal point for neurotoxicology within EPA and is
charged with the responsibility of devising means to detect and characterize neurotoxicity.
The primary goal of the Division is to provide the scientific basis and technological means
to be able to predict whether or not an environmental agent will produce neurotoxicity in
humans. In pursuit of this goal the division is organized in a multidisciplinary fashion with
research focused on six specific areas (1) methods development and validation, including
evaluation of existing methods, design and evaluation of new methods, and development of
testing strategies; (2) determination of the significance of variables that influence risk
assessment based on animal data, including environmental and organismal variables; (3)
developmental neurotoxicology, which evaluates the effects of developmental exposure on
structure and function of the nervous system; (4) research leading to a reduction in
uncertainties associated with quantitative dose-response determinations, including exposure
scenarios, compensation or adaptation during repeated dosing; (5) research leading to a
greater conceptual understanding of the neural substrate underlying neurobiological
endpoints; and (6) studies on specific neurotoxic agents, including heavy metals,
pesticides, industrial chemicals, and hazardous air pollutants. The use of known or
prototype neurotoxic chemicals has figured prominently in several of these research areas.
The research areas most impacted by the use of TET and TMT as prototype neurotoxicants
has been those of methods development, developmental neurotoxicology and specific agent
neurotoxicity characterization. Organotin research has had a minor impact on how
environmental / organismal variables and exposure scenarios impact the assessment of
neurotoxicity and have been least utilized in exploring mechanistic / conceptual issues in
neurotoxicology.
This deliverable summarizes the body of work conducted by NTD utilizing the
known or prototype neurotoxicants triethyltin (TET) and trimethyltin (TMT). Both
chemicals are triorganotin compounds and their study provides for interesting structure-
activity comparisons. TET has long been known as an agent that damages myelin but
leaves neurons unharmed while TMT causes neuronal loss in certain brain areas. Both
compounds damage the nervous system and are described as neuropathic. By definition a
compound that causes structural damage to the nervous system is considered a
neurotoxicant. A limited portion of the work was devoted to a characterization of the
neurotoxicity associated with tributyltin (TBT), an organotm of environmental concern.
NTD investigators have produced 56 papers on the organotin compounds of which 52 are
research papers and the remaining 4 are reviews. Although both were known for their
ability to cause specific types of structural damage to the nervous system the lack of a
thorough characterization of their neurotoxic profiles in the adult and developing rodent
prompted many of the NT]) investigators to determine the specific characteristics of the
neurotoxicity associated with acute exposure to TET and TMT. TET and TMT cause
cellular damage to the CNS and thus it is not surprising that many of the NTD papers
included a neuroanatomical assessment. Neuroanatomy was included as an endpoint of
study in its own right or was included to verify the morphological damage caused by the
organotin compound being studied. The use of neuroanatomical assessment as an adjunct
was particularily prevalent in papers using either compound as part of a methods
development strategy. These anatomical assessments ranged from the simple examination
2
-------
of brain and brain area weights to more sophisticated neuroanatomical methods involving
an evaluation of brain tissue at the light and electron microscopic level.
An examination of the NTD database on these two organotin compounds suggests
the known CNS actions of TET and TMT have been most profitably exploited by the
disciplines of behavior, electrophysiology and biochemistry in the areas of methods
development. All these disciplines within N1D have used TET and TMT as representatives
of the class of neurotoxicants that produce structural damage to the nervous system. Most
investigators chose an acute or semiacute dosing regimen because morphological alterations
can be demonstrated with both compounds after limited exposure. The working hypothesis
for NTD investigators was that a procedure or test being developed to detect neurotoxicity
should be able to identify a known neurotoxicant. Thus, these studies have provided critical
elements in the body of data used to shape many of the guidelines proposed or being
developed for neurotoxicity assessment. Both were used to cause defined damage to aid in
the development of new methods as well as in comparisons of existing methods for their
ability to detect neurotoxicity. Thus, data from these organotin studies have directly or
indirectly had an impact on several guidelines. These have included the proposed sensory
evoked potential, neuropathology, motor activity, functional observation battery test
guidelines and to a lesser extent the developmental neurotoxicology testing guideline. In
the future TET and TMT wifi serve as validation compounds that will aid in structuring the
test guideline to identify neurotoxicants causing learning and memory deficits.
Developmental neurotoxicity research at NTD was also a primary beneficiary of the
use of these prototype neurotoxicants. Studies with both compounds have shown the
feasibility of using a model of early postnatal exposure to assess the risk of developmental
neurotoxicity, although TET was utilized more often than TMT. These investigations have
demonstrated the surprising and permanent impact a chemical can have on brain
development after a limited exposure that does not alter somatic growth. Developmental
neurotoxicants can be identified using this early postnatal model which conveniently
avoids many of the complications inherent to in utero exposure models. NTD research has
demonstrated the feasibility of using behavioral measures, such as motor activity and
acoustic startle, to identify abnormal development of the CNS. Significant progress in the
development of biochemical methods to identify neurotoxicants also resulted from these
studies. Radioimmunoassays have been developed for proteins associated with the
different cell types of the CNS. The ontogeny of certain developmental processes is
mirrored in the developmental profiles of these proteins and perturbation of these processes
by neurotoxic insult is detected by an alteration in these profiles. In particular, it was
determined that assays of glial fibrillary acidic protein (GFAP), a protein associated with
astrocytes which increases in response to injury, may be applicable to first tier testing.
Developmental studies with both TET and TMT indicated that GFAP could be used to
identify compounds able to damage developing CNS as readily as they identified those
compounds damaging the adult brain. Developmental investigations with TET and TMT
also demonstrated the utility of a simple morphological measurement, brain weight, in
identifying agents that can disrupt CNS development. Finally, because NTD was actively
investigating the issue of the neurotoxicity associated with TET and TMT it was possible to
mount a rapid response to program office inquiries regarding the possible developmental
neurotoxicity of TBT, an organotin of environmental concern.
Methods development has proceeded in concert with an expansion of the database
on the CNS effects associated with TET and TMT and this existing database is a key
element in future research. This large body of work can be exploited in future research
directed at reducing uncertainty in risk assessment Future efforts should be targeted to an
exploration of issues related to exposure scenarios, quantitative dose-response relationships
and organismic / environmental variables that will aid not only in reducing the uncertainty
3
-------
in the prediction of neurotoxicity but will aid also in a greater conceptual understanding of
neurotoxicity and its mechanisms of action. Further, the specific structural alterations
caused by these organotins can be used to profitably explore basic function and
organization of the CNS as well as the relationshp between systemically induced
neurotoxicant damage and subsequent behavioral / functional alterations. In this way NTD
will continue to make profitable use of the known neurotoxic profiles of TET and TMT. In
summary, prototype neurotoxicants have and will continue to play a pivotal role in the NTD
goal of providing the means for the prediction of neurotoxicity.
4
-------
TABLE OF CONTENTS
page
Executive Summary 2
Introduction 10
Mission of NTD and Rationale for Using Prototype
Compounds
Definition of a Prototype Compound And Why Triethyltin and
Trimethyltin are Used as Prototype Neurotoxicants
Overview of Organotin compounds 11
Results 13
Relationship of NTD Organotin Work to NTD’s Mission
Conclusions 19
Future Research Directions 20
References 22
Appendix A: Annotation for Publications Resulting From This Project 26
Appendix B: Publications Resulting From This Project bound separately
1. Balaban, C. D., O’Callaghan, J. P., Billingsley, M. L. (1988). Trimethyltin induced
neuronal damage in the rat: Comparative studies using silver degeneration stains,
immunocytochemisiry and immunoassay for neurotypic and gliotypic proteins.
Neuroscience 26:337-361.
2. Boyes, W. K. and Dyer, R. S. (1983). Pattern reversal and flash evoked potentials
following acute triethyltin exposure. Neurobehav. Toxicol. Teratol. 5: 57 1-577.
3. Brock, T. 0. and O’Callaghan, J. P. (1987). Quantitative changes in the synaptic
vesicle proteins synapsin I and p38 and the astrocyte specific protein glial fibrillary
acidic protein are associated with chemical-induced injury to the rat central nervous
system. J. Neurosci. 7: 931-942.
4. Bushnell, P. J. (1990). Delay-dependent impairment of reversal learning in rats treated
with trimethyltin. Behavioral and Neural Biology IN PRESS.
5. Bushnell, P. J. (1988). Effect of delay, intertrial interval, delay behavior and
trimethyltin on spatial delayed response in rats. Neurotox. Teratol. 10: 237-244.
6. Chang, L. W. and Dyer, R. S. (1983). A time-course study of trimethyltin induced
neuropathology in rats. Neurobehav. Toxicol. Teratol. 5: 443-459.
7. Chang, L. W. and Dyer, R. S. (1983). Trimethyltin induced pathology in sensoly
neurons. Neurobehav. Toxicol. Teratol. 5: 673-696.
8. Chang, L. W. and Dyer, R. S. (1984). Trimethyltin induced zinc depletion in rat
hippocampus. In: The Neurobiology of Zinc. (C. Frederickson and G. Howell,
eds), Vol. 2. Alan R. Liss Series in Neurology and Neurobiology, pp. 275-290,
Alan R. Liss, Inc. New York.
9. Chang, L. W. and Dyer, R. S. (1985). Septo-temporal gradients of trimethyltin-
induced hippocampal damage. Neurobehav. Toxicol. Teratol. 7:43-49.
5
-------
10. Chang, L. W. and Dyer, R. S. (1985). Early effects of trimethyltin on the dentate
gyrus basket cells: A morphological study. J. Toxicol. Environ. Health 16: 641-
653.
11. Chang, L. W., Wenger, G. R., McMillan, D. E. and Dyer, R. S. (1983). Species
and strain comparison of acute neurotoxic effects of trimethyltin in mice and rats.
Neurobehav. Toxicol. Teratol. 5: 337-350.
12. Cook, L. L., Heath, S. M. and OCallaghan, J. P. (1984). Distribution of tin in brain
subcellular fractions following the administration of trimethyl tin and triethyl tin to
the rat. Toxicol. AppI. Pharmacol. 73: 564-568.
13. Cook, L. L., Jacobs, K. S. and Reiter, L. W. (1984). Tin distribution in adult and
neonatal rat brain following exposure to triethyltin. Toxicol. Appl. Pharmacol. 72:
75-8 1.
14. Cook, L. L., Stine, K. E., and Reiter, L. W. (1984). Tin distribution in adult rat
tissues after exposure to trimethyltin and triethyltin. Toxicol. Appi. Pharmacol. 76:
344-348.
15. Crofton, K., Dean, K., Menache, M. and Janssen, R. (1990). Trimethyltin effects
on auditoiy function and cochlear morphology. Toxicol. App. Pharmacol. IN
PRESS.
16. Crofton, K. M., Dean, K. F., Boncek, V. M., Rosen, M. B., Sheets, L. P.,
Chernoff, N. and Reiter, L. W. Prenatal or postnatal exposure to bis (tn-n-
butyltin) oxide in the rat; Postnatal evaluation and behavior. Toxicol. App.
Pharmacol. 97:113-123.
17. Dyer, R. S. (1987). Macrophysiological assessment of organometal neurotoxicity.
In H. A. Tilson and S. B. Sparber (eds.) Neurotoxicants and Neurobiological
Function: Effects of Organoheavy Metals. John Wiley and Sons, Inc. pp. 137-184.
18. Dyer, R. S. (1982). Physiological methods for assessment of trimethyltin exposure.
Neurobehavior. Toxicol. Teratol. 4: 659-664.
19. Dyer, R. S. and Boyes, W. K. (1984). Trimethyltin reduces recurrent inhibition in
rats. Neurobehav. Toxicol. Teratol. 6: 369-37 1.
20. Dyer, R. S. and Howell, W. E. (1982). Acute triethyltin exposure: effects on the
visual evoked potential and hippocampal afterdischarge. Neurobehav. Toxicol.
Teratol. 4: 259-266.
21. Dyer, R. S. and Howell, W. E. (1982). Triethyltin: ambient temperature alters visual
system toxicity. Neurobehavior. Toxicol. Teratol. 4: 267-27 1.
22. Dyer, R. S., Deshields, T. L. and Wonderlin, W. F. (1982) Trimethyltin-induced
changes in gross morphology of the hippocampus. Neurobehav. Toxicol. Teratol.
4:141-147.
23. Dyer, R. S., Howell, W. E. and Reiter, L. W. (1981). Neonatal triethyltin exposure
alters adult electrophysiology in rats. Neurotoxicology 2: 609-623.
6
-------
25. Dyer, R. S., Wonderlin, W. F. and Walsh, T. J. (1982). Increased seizure
susceptibility following trimethyltin administration in rats. Neurobehav. Toxicol.
Teratol. 4: 203-208.
26. Dyer, R. S., Walsh, T. J., Wonderlin, W. F. and Bercegeay, M. (1982). The
trimethyltin syndrome in rats. Neurobehav. Toxicol. Teratol. 4: 127-133.
27. Gordon, C. J., Long, M. D. and Dyer, R. S. (1984). Effect of triethyltin on
autonomic and behavioral thermoregulation of mice. Toxicol. App!. Pharmacol. 73:
543-550.
28. Howell, W. E., Walsh, T. J. and Dyer, R. S. (1982). Somatosensory dysfunction
following acute trimethyltin exposure. Neurobehav. Toxicol. Teratol. 4: 197-20 1.
29. Jacobs, K. S., Lemasters, J. J. and Reiter, L. W. (1983). Inhibition of ATPase
activities of brain and liver homogenates by triethyltin (TET). In Developments in
the Science and Practice of Toxicology, A. W. Hayes, R. C. Schnell and T. S.
Miya, Eds. Elsevier Science Publishers, B.V. pp. 517-520.
30. MacPhail, R. C. (1982). Studies on the flavor aversions induced by trialkyltin
compounds. Neurobehav. Toxicol. Teratol. 4: 225-230.
31. Miller, D. B. (1984). Pre- and postweaning indices of neurotoxicity in rats: Effects
of triethyltin (TET). Toxicol. App!. Pharmacol. 72: 557-565.
32. Miller, D. B., Eckerman, D. A., Krigman, M. R. and Grant, L. D. (1982). Chronic
neonatal organotin exposure alters radial-arm maze performance in adult rats.
Neurobehav. Toxicol. Teratol. 4: 185-190.
33. Miller, D. B. and O’Callaghan, J. P. (1984). Biochemical, functional and
morphological indicators of neurotoxicity: Effects of acute administration of
trimethyltin to the developing rat. J. Pharmacol. Exp. Ther. 231: 744-751.
34. Myers, R. D., Swartzwelder, H. S. and Dyer, R. S. (1982). Acute treatment with
trimethyltin alters alcohol self-selection. Psychopharmacology, 78: 19-22.
35. O Callaghan, J. P. and Miller, D. B. (1989). Assessment of chemically-induced
alterations in brain development using assays of neuron- and glia-localized proteins.
Neurotoxicol. 10:393-406.
36. O’Callaghan, J. P. and Miller, D. B. (1988). Acute exposure of the neonatal rat to
Iributylin results in decreases in biochemical indicators of synaptogenesis and
myelinogenesis. J. Pharmacol. Exp. Ther. 246: 394-402.
37. O’Callaghan, J. P. and Miller, D. B. (1988). Acute exposure of the neonatal rat to
triethyltin results in persistent changes in neurotypic and gliotypic proteins. J.
Pharmacol. Exp. Ther. 244: 368-378.
38. O’Callaghan, J. P. and Miller, D. B. (1984). Neuron-specific phosphoproteins as
biochemical indicators of neurotoxicity: Effects of acute administration of
trimethyltin to the adult rat. J. Pharmacol. Exp. Therap. 231: 736-743.
7
-------
39. O’Callaghan, J. P., Miller, D. B. and Reiter, L. W. (1983). Acute postnatal exposure
to triethyltm in the rat: Effects on specific protein composition of subcellular
fractions from developing and adult brain. J. Pharmacol. Exp. Ther. 224: 466-
472.
40. O’Callaghan, J. P., Niedzwiecki, D. M. and Means, J. C. (1989). Variations in the
neurotoxic potency of trimethyltin. Brain Research Bulletin 22: 637-642.
41. Peele, D. B., Farmer, J. D. and Coleman, J. E. (1989) Time-dependent deficits in
delay conditioning produced by trimethyltin. Psychopharmacology 97: 52 1-528.
42. Reiter, L. W. and Ruppert, P. H. (1984). Behavioral toxicity of trialkyltin
compounds: A review. Neurotoxicology 5: 177-186.
43. Reiter, L. W., Heavner, G. G., Dean, K. F. and Ruppert, P. H. (1981).
Developmental and behavioral effects of early postnatal expousre to triethyltin in
rats. Neurobehav. Toxicol. Teratol. 3: 285-293.
44. Reiter, L. W., Kidd, K., Heavner, G. and Ruppert, P. H. (1980). Behavioral toxicity
of acute and subacute exposure to triethyltin in the rat. Neurotoxicology 2: 97-112.
45. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1985). Development of locomotor
activity of rat pups exposed to heavy metals. Toxicol. Appl. Pharmacol. 78: 69-77.
46. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1984). Neurobehavioral toxicity of
triethyltin in rats as a function of age at postnatal exposure. Neurotoxicol. 5: 9-
22.
47. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1984). Trimethyltin disrupts acoustic
startle responding in adult rats. Toxicol. Lett. 22: 33-38.
48. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1983). Comparative developmental
toxicity of triethyltin using a split-litter and whole-litter dosing. J. Toxicol.
Environ. Health 12: 7 3-87.
49. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1983). Developmental and behavioral
toxicity following acute postnatal exposure of rat pups to trimethyltin. Neurobehav.
Toxicol. Teratol. 5: 42 1-429.
50. Ruppert, P. H., Walsh, T. J., Reiter, L. W. and Dyer, R. S. (1982). Trimethyltin-
induced hyperactivity: Time course and pattern. Neurobehav. Toxicol. Teratol.
4: 135-139.
51. Stanton, M. (199x). Neonatal exposure to triethyltin disrupts olfactory discrimination
learning in preweanling rats. CLEARED MANUSCRIPT.
52. Stanton, M. E., Jensen, K. F., Pickens, C. V. (199x). Neonatal exposure to
trimethyltin disrupts spatial delayed alternation learning in preweanling rats.
CLEARED MANUSCRIPT.
53. Stine, K. E., Reiter, L. W. and Lemasters, J. J. (1988). Alkyltin inhibition of
ATPase activities in tissue homogenates and subcellular fractions from adult and
neonatal rats. Toxicol. Appl. Pharmacol. 94: 394-406.
8
-------
54. Veronesi, B. and Bondy, S. (1986). Triethyltin-induced neuronal damage in
postnatally exposed rodents. Neurotoxicology, 7: 207-216.
55. Walsh, T. J., Miller, D. B. and Dyer, R. S. (1982) Trimethyltin, a selective limbic
system neurotoxicant, impairs radial-arm maze performance. Neurobehav.
Toxicol. Teratol. 4: 177-183.
56. Walsh, T. J., Gallagher, M., Bostock, E. and Dyer, R. S. (1982). Trimethyltin
impairs retention of a passive avoidance task. Neurobehav. Toxicol. Teratol. 4:
163-167.
9
-------
INTRODUCTION
Rationale for the Use of Prototype Compounds - The public is exposed to
a large number of chemicals - there are at least 65,000 used in daily commerce. However,
few of these chemicals have been evaluated for their neurotoxic potential. Twenty-five
percent of the chemicals that have been adequately evaluated have neurotoxic action (OTA,
1984; 1990). Periodic episodes involving large scale exposure of humans to compounds
such as tri-ortho-cresyl phosphate , methylmercury, Kepone and MPTP (Canon et al.,
1978; Kidd and Langworthy, 1933; Langston et aL, 1983; Takeuchi, 1968) with resulting
severe debilitation due to their neurotoxic effects, has highlighted the devastating
consequences of such exposures. In the last decade neurotoxicology has commanded a
growing importance and the increased need for hazard identification in this area of
toxicology has been noted by many groups and individuals (see Tilson, 1990 for a
discussion of the issues involved) (Reiter, 1980; Tilson, 1990; OTA, 1984; 1990). Thus,
it is critical for Environmental Protection Agency (EPA) as a regulatory agency to have at
its disposal the means to both detect and characterize potential neurotoxicants.
The Neurotoxicology Division (NTD) is the focal point within the EPA for studying
the effects of physical and/or chemical agents on the nervous system. Consistent with this
mission is the overall objective of providing the necessary scientific basis and technological
means to predict whether or not an environmental agent will produce neurotoxicity in
humans. Prediction of neurotoxicity is an important goal but equally important is
minimizing the uncertainty in such predictions. The general approach is to model human
neurotoxic disease in laboratory animals and then use data collected in these species to
make predictions about possible neurotoxic risks in humans. Investigators in NTD adapt,
develop or refine existing methods in pursuit of this goal. The Nil) approaches its
mission in a multidisciplinaiy fashion and investigation occurs at all levels of the neuraxis,
including neurobehavioral, neurochemical, neurophysiological and neuroanatomical.
Whole animal, cellular and molecular techniques are all applied in pursuit of the desired
objective. The field of neurotoxicology is a relatively young discipline and as a first step in
this endeavor many investigators in the NTD have chosen to use known or prototype
neurotoxicants to determine the feasibility of their particular approach for detecting and
characterizing neurotoxicity. Protocols designed to detect neurotoxic actions of unknown
compounds should detect known neurotoxicants, that is, known neurotoxiciants are used to
“validate” the test method (see Sette, 1987 for a discussion of this issue). Also consistent
with this plan of action is that many of the peer reviewers of the Nil) program have
sirongly urged all the principal investigators to test and validate their methodology by using
known neurotoxicants. In brief, prototype neurotoxicants were used and continue to be
used as positive controls or reference chemicals. Initially, many investigators in NTD
chose to use as positive controls the two organotins, triethyl- and trimethyltin. By
defmition any compound that causes structural damage to the nervous system is considered
a neurotoxicarn. When given systemically both TET and TMT produce damage to the CNS
and consequently have been described for many years as having “neurotoxic properties” or
as being “neuropathic”. Although both organotins are described as “neurotoxic” they have
distinctly different neurotoxicological profiles (see discussion below). Both have been
demonstrated to have neurotoxic action in humans.
Definition of a Prototype Compound and Why Triethyltin and
Trimethyltjn Are Used as Prototype Neurotoxic Compounds - A prototype is
something that can serve as a model or can be considered as an example of a particular
type. One definition of neurotoxicity is an alteration in the structural integrity of the
nervous system and by extension a compound that causes structural alterations would be
considered a neurotoxicant. Accordingly, both triethyltin and trimethyltin are considered to
be prototype neurotoxicants of the type that cause structural damage. The nervous system
10
-------
damage associated with each compound is clearly documented (see Overview section) and
thus both compounds appeared to be ideal candidates to aid in establishing the viability of a
multidisciplinary approach in accomplishing the mission of the Neurotoxicology Division.
Overview of Organotin Compounds in General with Emphasis on
Triethyltin and Trimethyltin - Organotins as their name implies are compounds
characterized by the presence of at least one covalent carbon-tin bond most organotins have
a teiravalent structure (Snoeij et al., 1987). These compounds have wide industrial and
agricultural applications as plastic stabilizers and catalysts, as miticides, algicides,
bacteriocides, fungicides and insecticides, and as wood and textile preservatives. The first
organotin compound was synthesized in 1852 by Lowig but wide spread commercial use
of these compounds has occurred primarily since the 1950s. There are currently three major
uses for the organotins: 1) heat stabilizers in polyvinyichioride polymers, 2) industrial and
agricultural biocides (Van der Kerk and Juijten (1954), and 3) industhal catalysts in a
number of chemical reactions (Van der Kerk, 1978). In recent years, tributyltin oxide
(TBT) has been of particular enviommental concern (see Laughlin & Linden, 1985 for a
discussion). TBT is an extremely effective antifouling agent and its incorporation into
marine paint to control growth of aquatic organisms has resulted in damage to more
sensitive aquatic species such as oysters. In 1986 EPA began a special review of
compounds containing TBT and their use is now more strictly regulated under the
Organotin Antifouling Paint Control Act of 1988. The commercial uses of TET and TMT,
as compared to TBT, have been quite limited and these two organotins are more generally
regarded as research tools. Many excellent reviews on the chemistry and uses of the
organotins as well as their enviornmental impact are available and these aspects of the
organotins will not be discussed further (Duncan, 1980; Hall & Pinkney, 1985; Hallas et
a!., 1982; Laughlin & Linden, 1985; Luijten, 1971; Maguire et a!., 1986; Piver, 1973;
Ross, 1965; Snoeij et a!., 1987)
The number and type of organic substituents determine the mammalian toxicity of
the organotins with triorganotins being more toxic than monoorganotins. However,
toxicity within a given class of organotins also varies and is determined by the number of
carbon atoms per side chain (Snoeij et al., 1987). Thus, in the series of iriorganotins, the
lower homologs, TET and TMT, are the most toxic while trioctyltin has little mammalian
toxicity (compare oral LD5O values in Table 1). The short-chain alkyltins, TET and TMT,
are the most neurotoxic while intermediate chain length compounds, such as tri-n-proplytin
or TBT are immunotoxic (Snoeij et aL, 1985). Until quite recently the acute toxic profile of
both TET and TMT has been described as one of trembling, irritation, twitching, loss in
body weight and progressive paralysis (Reiter & Ruppert, 1984; Tan and Ng, 1977).
However, it is now apparent that these two organotins have strikingly different pathological
proffles in adult organisms ((Brown et al., 1979).
TRIETHYLTIN - An extensive episode of poisoning by TET occurred in France
(Barnes & Stoner, 1959) resulting from the accidental inclusion of TET and monoethyltin
in a marketed product (Stalinon - preparation of diethyltin and linoleic acid) used to treat
skin infection. One hundred of the 219 persons poisoned died with the pathological
hallmark of this exposure being cerebral edema. Experimental exposure to TET results in
interstitial edema that is found throughout the white matter of both brain and spinal cord
and is the result of splitting and vacuolation of the myelin sheath at the interperiod line.
Cell loss does not appear to be a concommitant of TET intoxication (Magee et a!, 1957).
The myelin alterations and subsequent edema appear to be reversible if a nonlethal dose is
used and exposure is terminated..
11
-------
Table 1. Acute oral LD 50 values for various
organotin compounds in the rata
Compound LD 50
mono-n-butyltin trichloride 2200; 2300
di-n-butytin dichloride 219; 126; 112-182
tri-n-butyltin chloride 122; 349; 129
tetra-ri-butyltin > 4000
trimethyltin acetate 9
triethyltin acetate 4
tri-n-propyltin acetate 118
tri-n-butyltin acetate 380; 125-136
tri-n-octyltin acetate > 1000
aFrom Snoeij et al., 1987.
12
-------
TRIME THYL TIN - No cerebral edema is found after exposure to TMT but rather
the pathological consequences of TMT intoxication consists of neuronal damage primarily
within the hippocampus, amygdala, pyriform cortex, and neocortex (Brown et aL, 1979;
Bouldin et a!., 1981). Human exposure (Fortemps et a!., 1978; Ross et a!., 1981) results
in seizures, disorientation, insomnia, mental confusion, memory and learning impairments,
anorexia and emotional lability. These symptoms are suggestive of neurotoxic action but
no postmortem pathology data is available for humans. The vulnerability of the
hippocampus is evident in a variety of species including primates (Brown et al., 1984).
The pattern of hippocampal cell loss in the immature and adult rat is particularily striking
(see photomicrographs in Brock & O’Callaghan, 1987; Miller & O’Callaghan, 1984).
RESULTS
Relationship of the Investigation of Organotin Compounds to the
Overall Goals of NTD - Research in the Neurotoxicology Division focuses on the
following specific areas: (1) methods development and validation, this can include the
evaluation of existing methods, design and evaluation of new methods, and development of
testing strategies; (2) determination of the significance of variables that influence risk
assessment based on animal data, including environmental and organismal variables; (3)
developmental neurotoxicology, which evaluates the effects of developmental exposure on
structure and function of the nervous system; (4) research leading to a reduction in
uncertainties associated with quantitative dose-response determinations, including exposure
scenarios, compensation or adaptation during repeated dosing; (5) research leading to a
greater conceptual understanding of neurotoxicology, including mechanism of action and a
clear understanding of the neural substrate underlying neurobiological endpoints; and (6)
studies on specific neurotoxic agents that can include heavy metals, pesticides, industrial
chemicals, etc. The 56 studies conducted by NTD on the organotins (published or cleared)
are listed in the Appendix in annotated fonn. This annotation includes information
regarding the specifics of the study as follows: compound and dosing information; subject
information including species, sex, age; whether or not a time course was performed; the
method or methods employed; the research area or areas addressed; and a brief snynopsis
of the research. Fifty-two of these papers are research studies and the remaining 4 are
reviews; in this document all are referred to by the number they have in Appendix A.
As expected because of the known neurotoxic nature of TET and TMT, exposure to
either resulted in anatomical, behavioral, biochemical and electrophysiological alterations.
Exposure at any age produced deficits. Adults treated with TET showed reversible brain
edema and motor function deficits as well as alterations in evoked potential endpoints and
deficits in thermoregulatoiy capabilities (2, 27,44). Detectable levels of elemental tin are
found in brain and ATPase activity is inhibited after adult exposure to TET (12, 13, 14,
21, 53). None of the studies determining the effects of adult exposure to TET examined
the nervous system at the light or electron microscopic level. Conversely, many of the
studies characterizing the effects of adult exposure to TMT examined brain structures using
these techniques. The most dominant feature noted was cell loss in the pyramidal cell line
of the hippocampus although neuronal damage was found in other brain areas (1, 3, 4, 6,
7, 8, 9, 10, 11, 15, 18, 22, 26, 38, 40, 41, 50, 55). The CNS damage caused by TMT
can be detected by changes in neuronal and glial proteins associated with the specific cell
types of the nervous system (1, 3, 38, 40). Although elemental tin levels are elevated in
brain the distribution characteristics do not explain the regional susceptibility to this
neurotoxicant (12, 14). After exposure to TMT spontaneous seizures occur and
susceptibility to other agents causing seizures is increased (25, 26). Rats exposed to TMT
as adults are hyperactive, self-mutilate, and have deficient learning / memory capabilities
and altered arousal as indicated by changes in startle reflex and visual or somatosensory
evoked potentials (4, 5, 15, 24, 26, 28, 30, 32, 34, 41, 47, 50, 55, 56).
13
-------
Exposure of the neonate to either TET or TMT resulted in permanent brain weight
decreases that are accompanied by behavioral alterations including hyperactivity as well as
learning / memory deficits and a deficient reaction to stimulation (31, 32, 33, 35, 37, 39,
43, 45,46, 48, 49, 51, 52, 54). Early postnatal exposure to TMT resulted in a pattern of
pyramidal cell loss exactly like that found in adult (33, 35, 52). Although TET caused a
pennanent brain weight decrease with the greatest effect found in hippocampus no overt
cell loss was evident (37,39, 54). Alterations in adult electrophysiological endpoints were
found after neonatal exposure to TET; similar studies have not been performed after
neonatal exposure to TMT (23). Assays of neuronal and glial localized proteins indicated
both compounds cause damage to neurons and myelin when administered early in
development (33, 35, 37,38, 39). An increase in glial fibrillary acidic protein, an astrocyte
localized protein, accompanies this damage and indicates the developing CNS can respond
to injury in the same manner as the adult CNS (1, 3, 33, 35, 37).
An organization of the 52 research papers by compound, sex and whether it was an
adult or developmental study is presented in Table 2. Most of these papers are relevant to 1
or more research areas considered important to NTD (see Table 3 for a compilation of the
NTD studies on the organotins and the specific research area or areas they address). The
proportion of the 52 research papers utilizing a particular organotin compound, dosing
regimen and species is presented in Figure 1. Figure 2 presents the proportion of the 56
studies employing anatomy, behavior, biochemistry, electrophysiology, analysis or review
as the primary method. Papers emphasizing behavior as a primary endpoint often
employed other endpoints as well and the proportion of these behavioral papers using an
additional method is also presented in Figure 2.
The organization of the organotin papers in the above manner provides some
interesting information regarding the use of these prototype compounds by the NTD.
TMT was studied more often with 53% of the studies utilizing this compound as compared
to 31% for TET. However, when age of the subject at dosing is taken into consideration it
is evident that most of the TMT studies were conducted in adults (see Table 3). TET was
used more often than TMT in studies concerning developmental neurotoxicity. Rarely
(12%) were the effects of TMT and TET directly compared. A small percentage of the total
output (2 papers) concerned a characterization of the developmental neurotoxicity of TBT.
It is clear that the rat was the experimental subject of choice with 99% of the research
performed with this species. Male rats were always used if the study was concerned with
the effect of either TET or TMT in adults. With one exception (see Table 3) all
developmental studies determined the neurotoxicity of TET and TMT in both male and
female subjects; the 2 studies of TBT also utilized both sexes. Acute and subacute dosing
regimens were preferred; none of the 52 research papers employed a chronic treatment
regimen.
It is clear that behavioral methods were used more often in assessing and
characterizing the neurotoxicity of the three compounds (see the pie chart on the left side of
Figure 2). Almost half of the studies used behavioral methods with anatomy being the next
choice but accounting for a much lower percentage of the total (only 16.7%). However,
many of the investigators who used behavior as a primary endpoint also utilized additional
methods. When this is considered, anatomical endpoints (60%) were preferred with
biochemical, electrophysiological, or physiological methods being chosen less often (see
the pie chart on the right side of Figure 2). When research area is considered it is clear that
the bulk of the studies were concerned with either methods development or a specific
characterization of the neurotoxicity associated with the organotins (Table 3). In many
instances methods development and neurotoxicity characterization were conducted in the
same study. Developmental neurotoxicity was also a research area of major interest with
14
-------
Table 2. Breakdown of NTD Organotin Studies by Compound, Age and Sex.
I TET TMT TBT
[ Sex
Adult Developing Adult J
Developing If Adult Developing
male
only
2, 12, 13, 14,
20,21,27,29,
30, 44, 53
54
1, 3, 4, 5, 6, 7,
8, 9, 10, 11,
12, 14, 15, 19,
22, 24,25, 26,
28, 34, 38, 40,
41,47,50, 53,
55,56
female
only
16
both
sexes
13, 23,31,32,
37,39,43,45,
46,48,51, 53
30
32, 33,45,49,
52, 53
16,36
References in bold type appear in more than one category.
References # 17, 18, 35,42 are reviews.
-------
Table 3. NTD Research Areas and
Organotin Publications by NTD
Staff Addressing Each Area
Research Areas
Reference # in
Appendix
Methods development and validation
(MD)
1, 2, 3, 4, 5, 15, 20, 22, 23, 24,
30, 31, 33 37, 38, 39, 40,
41,43,44,45, 47,49,52,55
Environmental and organismal variables such
as sex, age, etc. that influence risk assessment
based on animal data
(EOV)
11,13, 16, 21, 26, 27, 30,
46, 53
Developmental neurotoxicity - eftects of
exposure to toxicants during development on
the structure and function of the nervous
system
(DEV)
16, 31, 32, 33, 36, 37,
46, 48,49, 51,
52, 54
Investigation of exposure scenarios,
dosing regimens and other variables related
to quanitative dose response determinations
that will lead to a reduction in the uncertainty
associated with extrapolation from laboratory
animal data
(DR)
12, 14, 32,40,44,48
Conceptual understanding of neurotoxicity -
includes research on mechanism of action and
neural substrates underlying neurobiological
endpoints
(CU)
4,5,14,19,33,37,50,51
Investigation of a specific neurotoxic agent
(SN)
6, 7, 9, 10, 15, 16, 24, 26,
27, 28, 29, 30,32, 34, 36,
38,43, 44, 47, 49, 50, 52,
54, 55, 56,
References in bold type are relevant to more than one research area. Abbreviations
appearing under research area are those used in the annotated reference list contained
in Appendix A.
16
-------
Figure 1.
Proportion of NTD Publications on Organotins
By Compound, Dosing Regimen, and Species
Compound
Dosing Regimen
Acute
E
Subacute
Species
LI
Rat
U
Mouse
N
‘-4
TMT
TET
U TBT
Li TMT&TET
-------
Figure 2.
Proportion of NTD Organotin Publications
By Primary Method
Proportion of Other Methods
Used in Behavioral Studies
7.2%
‘-4
Anatomy
Electrophysiology
LI Behavior
LI Biochemistry
a Analytical
Review
Anatomy
Electrophysiology
LI Behavior Alone
LI Biochemistry
Physiology
• Two or More
-------
methods development and neurotoxicant characterization counting heavily as topics of
interest in these studies. However, few of the studies investigated how dosing regimens,
exposure scenarios, or strain and species characteristics may influence the expression of the
neurotoxicity associated with the organotins. Variables of this type were most often
investigated in studies utilizing analytical techniques to determine the effects that age of the
subject and speciation of the compound had on tin levels in tissue. Even fewer studies
were directly concerned with investigating the mechanism of action of either TET or TMT.
CONCLUSION
This review of the Nil) work on the neuropathic compounds, TET and TMT,
indicates these prototypic neurotoxicants have aided and will continue to aid NT !) in
attaining its primary goal of providing the means for the assessment and prediction of
neurotoxicity. Utilized as research tools since the formation of the NTD in 1980 these
compounds have figured prominently in several important research areas of the NTD.
Specifically, they have played pivotal roles in methods development and developmental
neurotoxicology. In addition, they have been themselves the targets of detailed study that
has more thoroughly characterized their neurotoxic attributes. The behavioral, biochemical
and electrophysiological disciplines at ND) have benefited the most from the use of TET
and TMT in methods development. Both have figured prominently as part of the database
that has been utilized in the development of the formal guidelines for the evaluation of the
effects of pesticides and other toxic substances on the nervous system. These guidelines
include the use of a functional observational battery as well as tests for the assessment of
motor activity (EPA, 1983; 1985; 1987). Further, both have figured prominently in
establishing that visual evoked potentials (VEP) can be reliably altered by agents that cause
structural damage to the CNS (Boyes & Dyer, 1988) and thus have been an important
component of the database leading to the proposed test guidelines using sensory evoked
potential methods (Boyes, 1990).
The use of these prototype compounds has also been particularly beneficial in the
area of developmental neurotoxicology. Investigators at Nil) using both TET and TMT
have demonstrated the utility of the early postnatal exposure model for neurotoxicity
assessment in the developing organism. Because compounds are administered soon after
birth this model avoids many of the complicating factors associated with in utero exposure.
However, this model still allows exposure during a period of significant CNS
development. The postnatal model used in conjunction with both chemicals has proven
valuable in demonstrating that functional aberrations accompany neurotoxic insult during
development and thus have been instrumental in showing that behavioral procedures are
one possible means of identifying developmental neurotoxicants. The postnatal model used
in conjunction with both agents has shown the utility of assays of neurotypic and gliotypic
proteins as a biochemical means of identifying deviations in critical developmental prcesses
such as myelinogenesis and synaptogenesis. These assays also suggest TET damages
neurons as well as myelin and thus further suggests that the neurotoxicity profiles of TET
and TMT may be more similar during development than they are in the adult. However,
there is a lack of research addressing the issue of neuronal damage following adult
exposure to TET. Investigators at the Nil) have also demonstrated that the simple
morphological measure of brain weight can serve to identify a developmental
neurotoxicant. The effects of TET and TMT on brain weight were particularily surprising.
TET exposure in adults causes brain edema that results in an increase in brain weight.
Further, this edema and weight increase are reversible when exposure is terminated.
Developmental exposure to both TET and TMT cause permanent decreases in brain weight.
The extensive investigation of the developmental neurotoxicity of TET and TMT allowed a
rapid response of the NTD personnel to program office inquiries concerning the possible
19
-------
neurotoxicity of TBT. This organotin, although of environmental relevance, had little
significant developmental ñeurotoxicity compared to TET and TMT.
While the database on the developmental neurotoxicity of TET and TMT has been
generated using postnatal exposures this information has been used in determining the tests
to be used in the Collaborative Behavior Teratology Study (Adams et aL, 1985) and in the
structuring of the Developmental Neurotoxicity Guidelines (EPA, 1989). In both of these
protocols compounds were or will be evaluated for neurotoxic potential during in utero
exposure. The “generic” “developmental neurotoxicity protocol includes brain weight,
motor activity and auditory startle. It has also been suggested that EPA personnel further
evaluate the utility of the GFAP radioimmunoassay as a Tier 1 or “trigger” test for
developmental neurotoxicants (Francis et al., 1990; Rees et al., 1990). In summary,
NTD personnel have used TET and TMT to show the utility of brain weight as a simple
morphometric measurement that can provide an indication of brain dysmorphogenesis, the
utility of GFAP as a general quantitative, biochemical indicator of damage to both the
developing and adult nervous system, as well as the utility of the behavioral endpoints of
motor activity and auditory startle as an indicators of abnormal development.
FUTURE RESEARCH DIRECTIONS
The major uses of the organotins, TET and TMT, have been as positive controls or
known neurotoxicants in methods development and comparison of methods or as
compounds for additional neurotoxicity characterization. Often methods development has
proceeded in concert with an expansion of the database on the CNS effects associated with
TET and TMT. This further neurotoxicity characterization as well as the already available
database provides a large body of information that can be profitably exploited in future
research directed at reducing uncertainty in risk assessment. However, information is
lacking in certain areas and maximum use of the database will only occur if these data gaps
are alleviated. The current database concerns only the acute or subacute effects of TET and
TMT. This emphasis on acute rather than repeated exposure makes extrapolation from
acute to chronic exposure regimens difficult. Future work should be directed towards
exploring the problems that may be encountered in assessing neurotoxicity when exposure
to a toxicant is chronic-low level rather than acute or subacute. Although developmental
neurotoxicity has been a primary research area few studies have directly considered age or
other organismic / environmental variables as factors that may affect the expression of the
neurotoxicity associated with the organotins. There is a lack of comparable studies on the
effects of TET and TMT in the adult. In particular there are few studies examining
anatomical or behavioral effects after adult exposure to TET. Information on the age-
related neurotoxicity of the organotins will aid in using the database to address structure -
activity issues. A refinement of the current analytical techniques to allow a determination of
the speciated form of the organotin rather than levels of elemental tin will aid in the
investigation of distribution and metabolism of these compounds as well as structure -
activity questions. Few studies have attempted to determine the mechanisms by which each
of these organotins produces their selective profile of neurotoxicity. The lack of
mechanistic studies is not surprising; a necessary precursor is a thorough characterization
of the neurotoxicity of a compound as well as ways to manipulate its toxicity. The current
data base provides the neurotoxicity characterization of TET and TMT. The next step in
these mechanistic studies is to find ways to influence the expression of this neurotoxicity
(e.g., pharmacological manipulations, etc.). Future research targeted to an exploration of
issues related to exposure scenarios, quanitative dose-response relationships and
organismic / environmental variables will aid not only in reducing the uncertainty in the
prediction of neurotoxicity but will aid also in an exploration of the mechanisms of action
of these compounds and a greater conceptual understanding of neurotoxicity. In
20
-------
conclusion, prototype neurotoxicants have and will continue to play a pivotal role in the
NTD goal of neurotoxicity prediction.
21
-------
REFERENCES
Adams, J., Buelke-Sarn, J., Kinimel, C. A., Nelson, C. J., Reiter, L. W., Sobotka, T. J.,
Tilson, H. A. & Nelson, B. K. (1985). Collaborative behavioral teratology study:
Protocol design and testing procedures. Neurobehav. Toxicol. Teratol. 7: 579-586.
Barnes, J. M. and Stoner, H. B. (1959). Toxic properties of some dialkyl and trialkyl tin
salts. Br. J. md. Med. 15: 15-22.
Bouldin, T. W., Goines, N. D., Bagnell, C. R. and Krigman, M. R. (1981). Pathogenesis
of trimethyltin neuronal toxicity: Ultrastructural and cytochemical observations.
Am. J. Path. 104: 237-249.
Boyes, W. K. (1990). Prposed Test Guidelines for Using Sensory Evoked Potentials as
Measures of Neurotoxicity. EPA Deliverable # 2555.
Boyes, W. K. and Dyer, R. S. (1988). Visual Evoked Potentials as Indicators of
Neurotoxicity. EPA Deliverable # 2312A.
Brock, T. 0. and O’Callaghan, J. P. (1987). Quantitative changes in the synaptic vesicle
proteins synapsin I and p38 and the astrocyte specific protein glial fibrillary
acidic protein are associated with chemical-induced injury to the rat central nervous
system. 3. Neurosci. 7: 931-942.
Brown, A. W., Aidridge, W. N., Street, B. W. and Verschoyle, R. D. (1979). The
behavioral and neuropathological sequaela of intoxication byy trimethyltin
compounds in the rat. Am J. Path. 97: 59-81.
Brown, A. W., Verschoyle, R. D., Street, B. W., Aidridge, W. N. and Grindley, H.
(1984). The neurotoxicity of trimethyltin chloride in hamsters, gerbils and
marmosets. J. Appi. Toxicol. 4: 12-2 1.
Cannon, S. B., Veazey, J. M., Jr., Jackson, R. S., Burse, V. W., Hayes, C., Straub, W.
E., Landrigam, P. J. and Liddle, J. A. (1978). Epidemic kepone poisoning in
chemical workers. Amer. J. Epidemiol. 17: 529.
Criterion for a Recommended Standard: Occupational Exposure to Organotins. Washington
DC: National Institute of Occupational Saferty and Health, 1976.
Duncan, J. (1980). The toxicology of molluscicides. The organotins. Pharmac. Ther. 10:
407-429.
EPA Report No. 560/-6-76-011. The Manz4 acture and Use of Selected alkyltin
Compounds. 1976.
Francis, E. Z., Kimmel, C. A. and Rees, D. C. (1990). Workshop on the qualitative and
quantitative comparability of human and animal developmental neurotoxicity:
Summary and Implications. Neurotoxicol. Teratol. 12: 285-292.
Fortemps, E., Amand, G., Bomboir, S., Lauwerys, R. and Laterre, E. E. (1978).
Trimethyltin poisoning: report of two cases. Int. Arch. occup. envir. HIth. 41: 1-6.
22
-------
Hall, L. W. and Pinkney, A. E. (1985). Acute and sublethal effects of organotin
compounds on aquatic biota: an interpretative literature evaluation. CRC Toxicology
14: 159-209.
Hallas, L. E., Means, J. C. and Cooney, J. J. (1982). Methylation of tin by estuarine
microorganisms. Science 215: 1505-1507.
Kidd, J. G. and Langworthy, 0. R. (1933). Paralysis following the ingestion of Jamaica
ginger extreact adulterated with tri-ortho-cresyl phosphate. Johns Hopkins Med. J.
52: 39-66.
Langston, J. W., Ballard, P., Tetrud, J. W. and Irwin, I. (1983). Chronic parkinsonism in
humans due to a product of meperidine-analog synthesis. Science 219: 979-980.
Laughlin, R. B. and Linden, 0. (1985). Fate and effects of organotin compounds.
Ambio 14: 88-94.
Luijten, J. G. A. (1971). Applications and biological effects of organotin compounds. In:
Organotin Compounds (A.K. Sayer, ed.), pp. 93 1-974, Marcel Dekker Inc., New
York.
Magee, P. N., Stoner, H. B., and Barnes, J. M. (1957). The experimental production of
edema in the central nervous system of the rat by triethyltin compounds. J. Path.
Bact. 73: 107-124.
Maguire, R. J., Tkaez, R. J., Chau8, Y. K., Bengert, G. A., and Wong, P. T. S. (1986).
Occurrence of organotin compounds in water and sediment in Canada.
Chemosphere 15: 253-274.
McMillan, D. E. and Wenger, G. R. (1985). Neurobehavioral toxicology of trialkyltins.
Pharmacol. Rev. 37: 365-379.
Mushak, P., Krigman, M. R. and Mailman, R. B. (1982). Comparative organotin toxicity
in the developing rat: Somatic and morphological changes and relationship to
accumulation of total tin. Neurobehav. Toxicol. Teratol. 4: 209-215.
NIOSH Criteria for a Recommended Standard... .Occupational exposure to...organotin
compounds. DHEW Pub. No. 77-115. Washington, D. C.:U.S. Govn’t Printing
Office. Washington: 1976.
Office of Technology Assessment. (1990). Neurotoxicity: Identifying and controlling
poisons of the nervous system. OTA-BA-436.
Office of Technology Assessment. (1984). Impacts of neuroscience: Background paper.
OTA-BP-BA-24. Washington: U.S. Government Printing Office.
Piver, W. T. (1973). Organotin compounds: Industrial applications and biological
investigation. Environ. Health Perspect. 4: 6 1-79.
Rees, D. C., Francis, E. Z. and Kimmel, C. A. (1990). Scientific and regulatory issues
relevant to assessing risk for devleopmental neurotoxicity: An overview.
Neurotoxicol. Teratol. 12: 175-181.
23
-------
Reiter, L. W. (1983). Chemical exposures and animal activity: Utility of the figure-eight
maze. In: A. W. Hayes, R. C. Schnell, and T. S. Miya, eds. Developments in the
Science and Practice of Toxicology. Amsterdam: Elsevier Science Publishers.
Reiter, L. W. (1980). Neurotoxicology - meet the real world. Neurobehav. Toxicol.
2: 73-74.
Ross, A. (1965). Industrial application of organotin compounds. Ann. N. Y. Acad. Sci.
125: 107-123.
Ross, W. D., Emmett, E. A., Steiner, J. and Tureen, R. (1981). Neurotoxic effects of
occupational exposure to organotins. Am. J. Psychiats. 138:1092-1095.
Sette, W. F. (1987). Complexity of neurotoxicological assessment. Neurotox. Teratol.
9:411-416.
Snoeij, N. J., Penninks, A. H. and Semen, W. (1987). Biological activity of organotin
compounds: an overview.Environ. Research 44: 335-353.
Snoeij, N. J., Van lersel, A. A. J., Penninks, A. H. and Semen, W. (1985). Toxicity of
iriorganotin compounds: Comparative in vivo studies with a series of trialkyltrn
compounds and triphenyltin chloride in male rats. Toxicol. App!. Pharmacol. 81:
274-286.
Stoner, H. B., Barnes, J. M. and Duff, J. I. (1955). Studies on the toxicity of alkyltin
compounds. Br. J. Pharmacol. 10: 16-25.
Tan, L. P. and Ng, M. L. (1977). The toxic effects of trialkyltin compounds on nerve and
muscle. J. Neurochem. 29: 689-696.
Takeuchi, T. (1968). Pathologyh of Minamata disease. In: M. Katsuma, ed. Minamata
Disease, Study Group of Minamata Disease. Japan: Kumamoto University.
Tilson, H. A. (1990). Neurotoxicology in the 1990s. Neurtoxicol. Teratol. 12:293-300.
Torack, R. M., Gordon, J. and Prokop, J. (1970). Pathobiology of acute triethyltin
intoxication. In: International Review of Neurobiology, vol. 12, edited by C. C.
Pfeiffer and J. R. Smyuuthes. New York: Academic Press, pp. 45-86.
U. S. Environmental Protection Agency. (1989). Proposed amendments to the guidelines
for the health assessment of suspect developmental toxicants; request for
comments; notice. Fed. Regist. 54:9386-9403.
U. S. Environmental Protection Agency. (1985). Toxic Substances Control Act Testing
Guidelines. Federal Register 50: 39458-39460.
U. S. Environmental Protection Agency. (1983). Health Effects Test Guidelines. E.P.A.
560/6-83-001. PB83-257691. National Technical Information Service.
Van der Kerk, (3. J. M. (1978). The organic chemistry of tin. Chem. Tech. 8: 356-365.
Van der Kerk, G. J. M. and Luijten, J. G. A. (1954). Investigations on organotin
compounds. ifi. The biocidal properties of organotin compounds. J. App!. Chem.
4: 314-319.
24
-------
Watanabe, I. Organotms (Triethyltin) (l9xx). In Experimental and Clinical
Neurotoxicology, Spencer, P. S. and Schaumberg, H. H. (Eds.) Williams and
Wilkins, Blatimore, pp. 545-557.
25
-------
Appendix A: Publications (Annotated) resulting from this
Project.
1. Balaban, C. D., O’Callaghan, J. P., Billingsley, M. L. (1988). Trimethyltin induced
neuronal damage in the rat: Comparative studies using silver degeneration stains,
immunocytochemistry and immunoassay for neurotypic and gliotypic proteins.
Neuroscience 26:337-361. (TMT OH- acute, 8 mg/kg IF; salt rat, LE, male,
250-500 g; TC; MD*; ANAT, BIOCHEM; extent and degree of CNS damage
following TMT is area and time dependent, demonstrates utility of silver
degeneration stain technique, radioimmunoassays of proteins associated with glial
and neuronal constituents of nervous system in detecting CNS damage)
2. Boyes, W. K. and Dyer, R. S. (1983). Pattern reversal and flash evoked potentials
following acute triethyltin exposure. Neurobehav. Toxicol. Teratol. 5: 57 1-577.
(TET BR - acute, 0, 4.5, 6 mg/kg IP; salt; rat, LE, male, 220 - 360 g; No TC; MD;
ELEC;pauem reversal rather than flash evoked potentials were better at detecting
CNS alterations induced by TET)
3. Brock, T. 0. and O’Callaghan, J. P. (1987). Quantitative changes in the synaptic
vesicle proteins synapsin I and p38 and the astrocyte specific protein glial fibrillary
acidic protein are associated with chemical-induced injury to the rat central nervous
system. J. Neurosci. 7: 931-942. (TMT OH - acute, 0, 3, 6, 8, 9 mg/kg W;base;
rat, LE, male, 200-250 g; TC; MD; BIOCHEM, ANAT; because RIA values of
gliotypic and neuronotypic proteins are altered in a dose- and time-dependent
manner following damage induced by TMT they can be used to detect and
characterize CNS damage induced by other toxicants)
4. Bushnell, P. J. (1990). Delay-dependent impairment of reversal learning in rats treated
with trimethyltin. Behavioral and Neural Biology IN PRESS. (TMT OH - acute,
0,7 mg/kg IV; base; rat, LE, male, 350 g; TC; MD, CU; BEHAV, ANAT; TMT-
induced impairment in automaintained reversal learning was evident only if a delay
was incorporated into task, behavioral deficit not completely related to
morphological change)
5. Bushnell, P. J. (1988). Effect of delay, intertrial interval, delay behavior and
trimethyltin on spatial delayed response in rats. Neurotox. Teratol. 10: 237-244.
(TMT OH - acute, 0,7 mg/kg IV; base; rat, LE, male, 350 g; TC; MD, CU;
BEHAV, BIOCHEM; spatial delayed response task validated as a measure of
working memory and as a method for detection of toxicant-induced CNS damage,
RIA of GFAP, a gliotypic protein that increases in response to CNS damage, used
to quantify TMT-induced CNS injury)
6. Chang, L. W. and Dyer, R. S. (1983). A time-course study of trimethyltin induced
neuropathology in rats. Neurobehav. Toxicol. Teratol. 5: 443-459. (TMT CL -
acute, 0, 6 mg/kg OR; base, rat, LE, male, 60- 80 d; TC; SN; ANAT; descriptive
neuropathological assessment after TMT suggests limited damage to dentrate gyrus
area of hippocampus; the time course for pyramidal cell loss in hippocampus is
protracted, accompanied by gliosis and is more severe in the septal than temporal
portions)
26
-------
7. Chang, L. W. and Dyer, R. S. (1983). Trimethyltin induced pathology in sensory
neurons. Neurobehav. Toxicol. Teratol. 5: 673-696. (TMT Cl- acute, 0, 6 mg/kg
OR; base, rat, LE, male, 60- 80 d; TC; SN; ANAT; TMT is generally considered
to be a limbic system toxicant but descriptive neuropathological assessment at the
hght and electron microscopic level suggest damage to sensory neurons of retina,
inner ear, dorsal root ganglia, olfactory and pyriform cortices)
8. Chang, L. W. and Dyer, R. S. (1984). Trimethyltin induced zinc depletion in rat
hippocainpus. In: The Neurobiology of Zinc. (C. Frederickson and G. Howell,
eds), Vol. 2. Alan R. Liss Series in Neurology and Neurobiology, pp. 275-290,
Alan R. Liss, mc, New York.(TMT - acute, 0, 6 mg/kg IF; base; rat, SD, male,
200 g TC; SN; ANAT; descriptive neuropathological assessment at the light
microscopic level with cresyl violet stain and modified Timm’s method for heavy
metal staining suggest neuronal damage induced in hippocampus by TMT is
accompanied by a reduction or depletion of zinc in the mossy fibers of this area)
9. Chang, L. W. and Dyer, R. S. (1985). Septo-temporal gradients of trimethyltin-
induced hippocampal damage. Neurobehav. Toxicol. Teratol. 7:43-49.(TMT CL -
acute, 0, 6 mg/kg OR; base; rat, LE, male, 60-80 d; TC; SN; ANAT; descriptive
neuropathological assessment suggest damage by TMT to particular cells in
hippocampus depends on the location of the cell within the hippocampal formation
as well as subfield identity, granule cells are most affected at temporal pole, more
pyramidal cell loss occurs in the septal region)
10. Chang, L. W. and Dyer, R. 5. (1985). Early effects of trimethyltin on the dentate
gyrus basket cells: A morphological study. 1. Toxicol. Environ. Health 16: 641-
653. (TMT CI - acute, 0, 6 mg/kg OR; base; rat, LE, male, 60-80 d; No TC; SN;
ANAT; descriptive neuropathological assessment suggest alterations in dentate
gyms basket cells are observable by 24 hrs after TMT using electron but not light
microscopic techniques.)
11. Chang, L. W., Wenger, G. R., McMillan, D. E. and Dyer, R. S. (1983). Species
and strain comparison of acute neurotoxic effects of trimethyltin in mice and rats.
Neurobehav. Toxicol. Teratol. 5: 337-350. (TMT Cl - acute, 7.5 (rat) 3.0 (mouse)
mg/lcg.; base; rat, LE and SD; mouse, C57B1/6 and BALB/c, male, 60-90 day; No
TC; EOV; ANAT; descriptive neuropathological assessment suggests species and
strain differences in areas of hippocampal damage and neurological signs, mice
were more sensitive than rats and LE rats more sensitive than SD rats)
12. Cook, L. L., Heath, S. M. and O’Callaghan, J. P. (1984). Distribution of tin in brain
subcellular fractions following the administration of trimethyl tin and triethyl tin to
the rat. Toxicol. Appl. Pharmacol. 73: 564-568. (TET Br, TMT OH - acute, 6.0
mg/kg; base; rat, LE, male, 200- 250 g; TC; DR; ANALY; distributional profile
of tin in subcellular fractions of brain as measured by flameless atomic absorption
spectrometry varied as a function of the organic moiety, tin levels were lower,
persisted longer, and concentrated in mitochondrial fraction after TMT compared to
Th1
27
-------
13. Cook, L. L., Jacobs, K. S. and Reiter, L. W. (1984). Tin distribution in adult and
neonatal rat brain following exposure to triethyltin. Toxicol. Appi. Pharmacol. 72:
75-81.(TET Br - acute, 0, 3, 6, 9mg/kg IP; salt rat, CD, male, 60 d or male &
female, PND-5; TC; EOV; ANALY; tin levels as assessed by flameless atomic
absorption spectrometry were evenly distributed across brain areas, rate of
elimination did not vary as a function of age but concentration of tin in neonate
brain declined faster than adult because of brain growth)
14. Cook, L. L., Stine, K. E., and Reiter, L. W. (1984). Tin distribution in adult rat
tissues after exposure to trirnethyltin and triethyltin. Toxicol. Appl. Pharmacol. 76:
344-348. (TET Br , TMT OH - acute 3, 6, 9 mg/kg IP (TET only 6 mg/kg), base;
rat, LE, male, 60 d TC; DR, CU; ANALY; tin levels and rates of elimination as
assessed by flameless atomic absorption spectrometry were greater in all tissues
following TET as compared to TMT, brain area distributions of tin following TMT
were equivalent so distribution differences do not acount for the region-specific
pathology associated with TMT)
15. Crofton, K., Dean, K., Menache, M. and Janssen, R. (1990). Trimethyltin effects
on auditory function and cochlear morphology. Toxicol. App. Pharmacol. IN
PRESS. (TMT OH - acute 3, 5, 7 mg/kg, base; rat, LE, male, 60 d; No TC; MD,
SN; BEHAV, ELEC; ANAT; TMT causes histopathological changes in inner ear -
cochlear hair cell loss - associated with auditory dysfunction detectable by auditory
startle reflex and brainstem auditory evoked response methodology)
16. Crofton, K. M., Dean, K. F., Boncek, V. M., Rosen, M. B., Sheets, L. P.,
Chernoff, N. and Reiter, L. W. Prenatal or postnatal exposure to bis (tn-n-
butyltin) oxide in the rat; Postnatal evaluation and behavior. Toxicol. App.
Phannacol. 97:113-123. (TBTO - subchronic 0, 2.5, 5, 10, 12, 16 mg/kg from GD
6- 20 or acute 0,40,50,60 mg/kg PND5, salt; rat, LE, female & male; TC; DEV,
SN, EOV; BEHAV, TERATOL, TOXICOL, ANAT;prenatal TBTO caused effects
in Chernoff-Kavlock postnatal teratology screen only at maternally toxic doses,
postnatal exposure caused brain weight decreases and behavioral alterations at only
at doses causing pup mortality)
17. Dyer, R. 5. (1987). Macrophysiological assessment of organometal neurotoxicity.
In H. A. Tilson and S. B. Sparber (eds.) Neurotoxicants and Neurobiological
Function: Effects of Organoheavy Metals. John Wiley and Sons, Inc. pp. 137-184.
(TET, TMT - REV; ELEC; macrophysiological techniques such as EEG, evoked
potential, kindling and afterdischarge, drug-induced, and maximal-electroshock
seizures can be used to further characterize the neurotoxicity of TET and TMT)
18. Dyer, R. S. (1982). Physiological methods for assessment of trimethyltin exposure.
Neurobehavior. Toxicol. Teratol. 4: 659-664. (TMT - REV; ELEC; gross
physiological measures of limbic system function are not as efficient at detecting
TMT damage as intrahippocampal evoked potentials, preliminary neuropathological
descriptions are not adequate to direct physiological studies and result in an
inadequate characterization of neurotoxicity)
19. Dyer, R. S. and Boyes, W. K. (1984). Trimethyltin reduces recurrent inhibition in
rats. Neurobehav. Toxicol. Teratol. 6: 369-371. (TMT OH - acute 0, 5, 6 mg/kg
OR,base; rat, LE, male;TC; CU; ELEC; TMT reduces recurrent inhibition in
hippocampus within 2 hours of dosing suggesting that increased activity in mossy
fibers is a result of reduced basket cell inhibition of the dentate granule cells)
28
-------
20. Dyer, R. S. and Howell, W. E. (1982). Acute triethyltin exposure: effects on the
visual evoked potential and hippocampal afterdischarge. Neurobehav. Toxicol.
Teratol. 4: 259-266.(TET Br - subchronic 0, .188, .375, .75, 1.5 mg/kg/day IP for
6 days; rat, LE, male; TC; MD; ELEC; both visual evoked response (VER) and
hippocampal afterdischarge (AD) can detect acute effects of TET, VER changes
indicate myelinopathy and/or CNS depression, threshold change was the most
sensitive AD measure)
21. Dyer, R. S. and Howell, W. E. (1982). Triethyltin: ambient temperature alters visual
system toxicity. Neurobehavior. Toxicol. Teratol. 4: 267-271.(TET Br - acute
0,3,6,9 mg/kg IP; rat, LE, male; TC; EOV; ELEC; TET caused dose-related
hypothermia and increased visual evoked response latencies, preventing
hypothermia by maintainance in a warmer temperature worsened
electrophysiological signs of neurotoxicity)
22. Dyer, R. S., Deshields, T. L. and Wonderlin, W. F. (1982) Tnmethyltin-induced
changes in gross morphology of the hippocampus. Neurobehav. Toxicol. Teratol.
4:141-147. (TMT Cl - acute, 0,5,6,7 mg/kg OR; base; rat, LE, male, 50 - 60 d; TC;
MD; ANAT; comparison of simple anatomical methods (length of pyramidal cell
line and thickness of dentate gyms (DG), granule cell layer, CAl, CA3, intrahilar
areas of DG) to evaluate the morphological changes caused by TMT indicate the
most clearly dose-related was length of pyramidal cell line from CA1-CA3)
23. Dyer, R. S., Howell, W. E. and Reiter, L. W. (1981). Neonatal triethyltin exposure
alters adult electrophysiology in rats. Neurotoxicology 2: 609-623. (TET Br -
acute, 0, 3,6,9 mg/kg IP; salt, rat, SD, male & female, PND5; No TC; MD; DEV;
ELEC; visual evoked potentials (VEPS); when tested as adults hippocampal
afterdischarges, picrotoxin and pentylenetetrazol seizure susceptibility indices show
VEP is sensitive to perinatal toxicant exposure)
24. Dyer, R. S., Howell, W. E. and Wonderlin, W. F. (1982). Visual system dysfunction
following acute trimethyltin exposure in rats. 4: 191-195. (TMT Cl- acute,
0,4,5,6,7 mg/kg OR; base; rat, LE, male, 60 d; TC; SN, MD; ELEC; TMT causes
visual system damage that is detected by visual evoked responses (VER), VER
changes suggest alterations in retinal processing and arousal)
25. Dyer, R. S., Wonderlin, W. F. and Walsh, T. J. (1982). Increased seizure
susceptibility following trimethyltin administration in rats. Neurobehav. Toxicol.
Teratol. 4: 203-208. (TMT Cl- acute, 0, 5, 6,7 mg/kg OR; base; rat, LE, male,
277 - 284 g; TC; SN, MD; ELEC; TMT increased seizure indices in all models
(behavioral scoring, hippocampal and amygdaloid kindling, sensitivity to
pentylenetetrazol-induced seizures, afterdischarge threshold) in a dose-related
manner)
26. Dyer, R. S., Walsh, T. J., Wonderlin, W. F. and Bercegeay, M. (1982). The
trimethyltin syndrome in rats. Neurobehav. Toxicol. Teratol. 4: 127-133.(TMT Cl-
acute, 0, 1 - 10 mg/kg OR or IP; base; rat, LE, male, 200 - 600 g; TC; EOV, SN;
BEHAV, TOXICOL, PHYSIOL, ANAT; TMT exposure causes unique syndrome
that includes spontaneous seizures, tail mutilation, vocalization, weight and/or age
appear to determine degree of toxicity (death and weight loss)
29
-------
27. Gordon, C. J., Long, M. D. and Dyer, R. S. (1984). Effect of triethyltin on
autonomic and behavioral thermoregulation of mice. Toxicol. App!. Pharmacol. 73:
543-550. (TET Br - acute, 0, 2,4, 6, 8 mg/kg IF; salt; mouse; BALB/c, male,
young adult TC; EOV, SN; BEHAV; PHYSIOL; TET results in hypothermia, no
change in evaporative water loss, a decrease in metabolic rate and a preference for
cooler temperatures suggesting altered thermoregulation)
28. Howell, W. E., Walsh, T. J. and Dyer, R. S. (1982). Somatosensory dysfunction
following acute trimethyltin exposure. Neurobehav. Toxicol. Terato!. 4: 197-201.
(TMT Cl - acute, 0,7 mg/kg OR; base; rat, LE, male, 320 - 540 g; TC; SN;
BEHAV, ELEC; TMT alters somatosensoiy function as shown by increased
latency to respond to a heat stimulus, increased somatosensory evoked responses,
but no change in peripheral nerve function [ conduction velocity and threshold] and
suggests TMT causes central but not peripheral damage)
29. Jacobs, K. S., Lemasters, J. J. and Reiter, L. W. (1983). Inhibition of ATPase
activities of brain and liver homogenates by triethyltin (TET). In Developments in
the Science and Practice of Toxicology, A. W. Hayes, R. C. Schnell and T. S.
Miya, Eds. Elsevier Science Publishers, B.V. pp. 5 17-520. (TET Br - acute, 0, 6
mg/kg fl); rat, SD, male; TC; SN; BIOCHEM, ANALY; TET more effectively
inhibits liver than brain ATPase when given in vivo)
30. MacPhail, R. C. (1982). Studies on the flavor aversions induced by trialkyltin
compounds. Neurobehav. Toxicol. Teratol. 4: 225-230. (TMT OH - Repeated, 0,
.625, 1.25, 2.5, 5.0 mg/kg x 3 IP; base; TET Br - acute, 0, .375, .75, 1.5, 3.0 IP
or repeated, 0,.188, .375, .75, 1.5 mg/kg IP x 5 or 6 or acute, 0, 5 mg/kg IP; base;
rat; LE, male (TET, TMT) female (TMT); TC; MD, EOV, SN; BEHAV; TET and
TMT both result in flavor aversions (FA) that are dependent on both the dose and
number of pairings of the toxicant and flavor, doses of TET or TMT required to
produce FA are at least 25 - 45% of the LD-50 values, sex was not a factor in
development of FA to TMT and familiarity with test chamber did not alter FA to
IEI)
31. Miller, D. B. (1984). Pre- and postweaning indices of neurotoxicity in rats: Effects
of triethyltin (TET). Toxicol. App!. Pharmacol. 72: 557-565. (TET Br - acute, 0, 3,
6 mg/kg IP; salt; rat, LE, male & female, PND5; TC; ;DEV, MD; BEHAV;
ANAT; TET alters function during life span as evidenced by alterations in
preweaning, juvenile and adult activity (automated and open-field) and learning
(alleyway conditioning and radial arm maze), preweaning deficits can be detected
by tailoring tasks to limited capabilities of neonates, TET causes permanent
decreases in whole brain, hippocampus and cerebellum weights with hippocampus
most affected)
32. Miller, D. B., Eckerman, D. A., Krigman, M. R. and Grant, L. D. (1982). Chronic
neonatal organotin exposure alters radial-arm maze performance in adult rats.
Neurobehav. Toxicol. Teratol. 4: 185-190. (TET sulfate or TMT OH semichronic
0,0.3, 1.0 mg/kg OR PND 3-29, TMT 1.0 mg/kg every other day; rat; LE; male &
female; No TC; DEV, SN, DR; BEHAV; rats given TET were more active, took
longer to reach criterion and showed a transient deficit in accuracy when tested as
adults in radial arm maze)
30
-------
33. Miller, D. B. and OCallaghan, J. P. (1984). Biochemical, functional and
morphological indicators of neurotoxicity: Effects of acute administration of
tnmethyltin to the developing rat. J. Pharmacol. Exp. Ther. 231: 744-751.(TMT
OH - acute, 0,5,6 mg/kg IP; base; rat, LE, male & female; PND5; TC; DEV, MD,
CU; BIOCHEM, BEHAV, ANAT; TMT interferes with brain development as
mdicated by dose and time dependent alterations in a synapse-localized
phosphoprotein, permanent decreases in brain, hippocampus and cerebellum
weights, loss of hippocampal CA3-4 pyramidal cells and behavioral dyfunctions
mcluding hyperactivity and compromised learning (alleyway conditioning, passive
avoidance, radial-arm maze;demonstrates utility of multi-endpoint and timepoint
strategy for detection and characterization of neurotoxicity)
34. Myers, R. D., Swartzwelder, H. S. and Dyer, R. S. (1982). Acute treatment with
trimethyltin alters alcohol self-selection. Psychopharmacology, 78: 19-22. (TMT
CL - acute, 0,7 mgllkg OR; base; rat, LB. male; 348 -460 g; No TC; SN;
BEHAV; ANAT; compared to controls TMT-treated rats consummed markedly
less alcohol, regardless of concentration, whether selection occurred in the home-
cage or a food contingent schedule-induced polydypsia situation, effects not due to
changes in gustatory sensitivity but may be related to damage of forebrain
structures)
35. O’Callaghan, J. P. and Miller, D. B. (1989). Assessment of chemically-induced
alterations in brain development using assays of neuron- and glia-localized proteins.
Neurotoxicol. 10:393-406. (TBT, TET, TMT - REV; BIOCHEM, ANAT;
reviews the use of neuron- and glial-localized proteins in detecting neurotoxic insult
to the developing nervous system; known neurotoxicants such as TET and TMT
were used to damage developing brain; significant changes in these proteins can be
observed in the absence of cytopathology or decreases in brain weight; the
astrocyte-localized protein, glial fibrillary acidic protein, increases in response to
chemically induced brain injury in the neonate as well as in the adult)
36. O’Callaghan, 3. P. and Miller, D. B. (1988). Acute exposure of the neonatal rat to
tributylin results in decreases in biochemical indicators of synaptogenesis and
myelinogenesis. J. Pharmacol. Exp. Ther. 246: 394-402. (TBT oxide - acute, 0, 2,
3,4,5 mg/kg IP; base; rat, LE, male & female; PND5; TC; DEV, SN;
BIOCHEM, ANAT; TBT caused decreases in the synapse-localized protein, p38,
and the oligodendroglial protein, myelin basic protein, in hippocampus and
cerebellum that did not persist into adulthood at doses that did not alter brain,
thymus or body weight; shows neurotoxicity can be detected by assays of
neurotypic and gliotypic proteins in the absence of overt changes in morphology,
TBT is not as neurotoxic as TET or TMT)
37. O’Callaghan, 3. P. and Miller, D. B. (1988). Acute exposure of the neonatal rat to
triethyltin results in persistent changes in neurotypic and gliotypic proteins. 3.
Pharmacol. Exp. Ther. 244: 368-378. (TET Br - acute, 0, 3, 6 mg/kg IP; salt; rat,
LB. male & female; PND5; TC; DEV, MD, CU; BIOCHEM, ANAT; TET caused
permanent brain and brain area weight decreases, permanent alterations in proteins
associated with specific developmental processes [ e.g., synaptogenesis,
myelinogenesis, etc] show utility of assays of neuro and gliotypic proteins in
neurotoxicity assessment, increases in the astrocyte-associated protein, glial
fibrillary protein, show developing nervous system responds to CNS damage in a
manner similar to adult brain)
31
-------
38. O’Callaghan, J. P. and Miller, D. B. (1984). Neuron-specific phosphoproteins as
biochemical indicators of neurotoxicity: Effects of acute administration of
trimethyltin to the adult rat. J. Pharmacol. Exp. Therap. 231: 736-743.(TMT OH -
acute, 0, 6, 8,9 mg/kg IV; base; rat, LE, male; 175-225 g; TC; MD, SN;
BIOCHEM, ANAT; TMT caused dose- and time-related decreases in hippocampal
phosphoproteins and changes were still evident 14 weeks following dosing and
suggests neuronal phosphoproteins may be used as biochemical indicators of
neurotoxicity)
39. O’Callaghan, J. P., Miller, D. B. and Reiter, L. W. (1983). Acute postnatal exposure
to tnethyltin in the rat: Effects on specific protein composition of subcellular
fractions from developing and adult brain. J. Pharmacol. Exp. Ther. 224: 466-
472. (TET Br - acute, 0, 3, 6 mg/kg IP; salt; rat, LE, male & female; PND5; TC;
DEV, MD; BIOCHEM, ANAT; TET caused permanent dose-related decreases in
brain weights and alterations in the phosphoprotein, myelin basic protein
suggesting alterations in myelinogenesis)
40. O’Callaghan, J. P., Niedzwiecki, D. M. and Means, J. C. (1989). Variations in the
neurotoxic potency of trimethyltin. Brain Research Bulletin 22: 637-642. (1’MT OH
or Cl - acute, 0, 8 mg/kg IV; base; rat, LE, male; 40 d; No TC; DR, MD;
BIOCHEM, ANALY; 7 commercially available sources of TMT specified at
greater than 95% pure produced varying degrees of CNS damage as revealed by
changes in histology, hippocampal weight and concentration of the astrocyte
protein, glial fibrillary acidic protein; analysis of samples for organotm content as
well as contaminants confirmed that the decreases in neurotoxicity could be
attributed to sample to sample variation in TMT content)
41. Peele, D. B., Farmer, J. D. and Coleman, J. E. (1989) Time-dependent deficits in
delay conditioning produced by trimethyltin. Psychopharmacology 97: 52 1-528.
(TMT OH - acute, 0, 8 mg/kg IV; base; rat, LE, male, 40 d; TC; MD; BEHAV,
ANAT; TMT resulted in passive avoidance and taste aversion conditioning deficits
when delay was incorporated as part of the test, TMT did not affect taste
discrimination and because similar delay dependent effects were evident in both
learning tests suggests these are true deficits in memorial processes rather than due
to effects of TMT on sensory, motor or associative processes)
42. Reiter, L. W. and Ruppert, P. H. (1984). Behavioral toxicity of trialkyltin
compounds: A review. Neurotoxicology 5: 177-186. (TMT, TET - REV; BEH;
review of the symptomatology reported after human exposure to TET and TMT
with a comparison of the functional or behavioral alterations that accompany
exposure to TET and TMT in the adult nonhuman organism)
43. Reiter, L. W., Heavner, 0. 0., Dean, K. F. and Ruppert, P. H. (1981).
Developmental and behavioral effects of early postnatal expousre to iriethyltin in
rats. Neurobehav. Toxicol. Teratol. 3: 285-293. (TET Br - acute, 0, 3, 6, 12 mg/kg
IP; salt; rat, SD, male & female, PND5; TC; DEV, MD, SN; BEHAV, ANAT;
tests for physical maturation, development of reflexes, motor coordination, motor
activity accompanied by measurement of brain weight indicate TET interferes with
CNS development as suggested by delayed development of rope descent and
locomotion, persistent increases in motor activity as adults and a permanent brain
weight decrease)
32
-------
44. Reiter, L. W., Kidd, K., Heavner, G. and Ruppert, P. H. (1980). Behavioral toxicity
of acute and subacute exposure to triethyltin in the rat. Neurotoxicology 2:97-112.
(TET Br - acute, 0, 1.5, 3.0 mg/kg SC or subchronic 0, 5, 10, 15, 20 mg/liter for 3
wks DW, 0, 8.4, 13.9, 17.3 mg/kg total intake, salt, rat, SD, male, 90-120 d, TC,
DR, SN, MD; BEIIAV, ANAT, TOXICOL; acute and subacute dosing with TET
causes decrements in motor activity, open field behavior, acoustic startle response
and landing foot spread that are reversible within 1 month after dosing ceases,
BEHAV changes occurred as doses not affecting growth or reducing food and
water intake; dose related increases in brain but not other organ weights accompany
subacute exposure)
45. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1985). Development of locomotor
activity of rat pups exposed to heavy metals. Toxicol. App!. Pharmacol. 78: 69-77.
(TET BR - acute, 0,4,5,6 mg/kg IP; salt; TMT OH - acute, 0, 4, 5, 6 mg/kg IP;
base; rat; LE; male & female, PND5; TC; MD, DEY; BEHAV; treatment with TET
and TMT caused hyperactivity to develop by the end of the preweaning period and
suggest preweaning assessment of locomotor activity would be predictive of
juvenile or adult activity changes)
46. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1984). Neurobehavioral toxicity of
triethyltin in rats as a function of age at postnatal exposure. Neurotoxicol. 5: 9-
22. (TET BR - acute, 0, 1.5, 3.0, 6.0 mg/kg IP; salt; rat; SD; male & female,
PND1, 5, 10, 15; TC; EOV, DEV; SN; BEHAV,TOXICOL; ANAT;
developmental toxicity depended on day of exposure, all exposure days resulted in
preweaning growth retardation but only PND5 exposure produced a permanent
brain weight decrease, increased seminal vesicle weights and behavioral deficits that
included preweaning deficits in rope descent and adult hyperactivity)
47. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1984). Trimethyltin disrupts acoustic
startle responding in adult rats. Toxicol. Lett. 22: 33-38. (TMT OH - acute, 0, 4, 5,
6 mg/kg IP; base; rat; LE; male, 60 d; TC; MD, SN; BEHAV; all doses of TMT
reduced the number of responses, response amplitude and sensitization by
background noise while response latency was increased, deficits occurred within 2
bra of dosing and were still evident 4 weeks later, because hippocampa! lesions do
not produce this pattern of deficits it is unlikely TMT-induced limbic system
damage can account for these effects, more likely they are due to damage to the
primary auditory startle circuit)
48. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1983). Comparative developmental
toxicity of triethyltin using a split-litter and whole-litter dosing. J. Toxicol.
Environ. Health 12: 73-87.(TET BR - acute, 0,3,6,9 mg/kg IP; salt; rat; SD; male
& female, PND5; TC; DR. DEV; BEHAV, ANAT, TOXICOL; whole- or split-
litter dosing models did not alter the effects of TET on mortality, brain weight or
postweaning body weight but split-litter pups did have more persistent preweaning
growth deficits and were more hyperactive, suggests dosing regimen is not a
primary determinent of the development toxicity of TET
33
-------
49. Ruppert, P. H., Dean, K. F. and Reiter, L. W. (1983). Developmental and behavioral
toxicity following acute postnatal exposure of rat pups to trimethyltin. Neurobehav.
Toxicol. Teratol. 5: 421-429. (TMT OH - acute, 0, 4, 5, 6 mg/kg IP; base; rat; LE;
male & female, PND5; TC; DEV, MD, SN; BEHAV, ANAT, TOXICOL; body
growth was retarded only during the preweaning period and organ weights were
not affected but TMT caused permanent dose-related decreases in whole brain,
hippocarnpus and olfactory bulb weights, as adults TMT treated animals were
hyperactive and had alterations in the acoustic startle response)
50. Ruppert, P. H., Walsh, T. J., Reiter, L. W. and Dyer, R. S. (1982). Trimethyltin-
induced hyperactivity: Time course and pattern. Neurobehav. Toxicol. Teratol.
4: 135-139. (TMT CL - acute, 0, 5, 6,7 mg/kg OR; base; rat; LE, male, 60 d; TC;
CU, SN; BEHAV, ANAT; an examination of the role of chemically induced
hippocampal damage in the genesis of hyperactivity, clear hyperactivity was present
by 4 days after dosing and still apparent at 32 days but only for the 7 mg/kg group,
all doses caused hippocampal damage as indicated by a decrease in the length of the
pyramidal cell line, hyperactivity was not related to the degree of hippocampal
damage and may be due to damage in other brain areas)
51. Stanton, M. (199x). Neonatal exposure to triethyltin disrupts olfactory discrimination
learning in preweanling rats. CLEARED MANUSCRIPT. (TET SUL - acute, 0, 3,
5 mg/kg IP; base; rat, LE, male & female, PND5, 10, 16; TC; DEV, CU;
BEHAV, ANAT; olfactory discrimination deficits in TET-treated rats suggest an
early impairment of associative learning and changes in nonassociative processes
were not the cause; age of exposure and testing interacted to produce differential
effects on learning, brain weight was decreased by 5 mg/kg TET on all days of
exposure with the greatest decrease after PND5 TET; data suggests a dissociation
of the behavioral, neural and somatic effects of TET)
52. Stanton, M. E., Jensen, K. F., Pickens, C. V. (199x). Neonatal exposure to
trimethyltin disrupts spatial delayed alternation learning in preweanling rats.
CLEARED MANUSCRIPT. (TMT OH - acute, 0,6 mg/kg IP; base; rat, LE, male
& female, PND1O; No TC; MD, DEV, SN BEHAV, ANAT; during the
preweaning period TMT-ireated pups were unable to learn a discrete-trials delayed
alternation T-maze task but could learn a simple position discrimination suggesting
motor abnormalities were not a determinant of the deficient performance; spatial
working memory deficits can be detected during the preweaning period and may be
predictive of adult spatial working memory deficits; light microscopic examination
showed loss of pyramidal cells and reduction in size of hippocampus after TMT).
53. Stine, K. E., Reiter, L. W. and Lemasters, J. J. (1988). Alkyltin inhibition of
ATPase activities in tissue homogenates and subcellular fractions from adult and
neonatal rats. Toxicol. Appl. Pharmacol. 94: 394-406. (TET BR - acute, 0, 6
mg/kg IP; TMT BRjat CD, male, 60 D; male & female, PND5; TC; EOV
BIOCHEM; higher concentrations of TET are necessary to inhibit mitochondrial
ATPase in adult brain homogenates than in neonatal brain or isolated brain
mitochondria the tin concentrations in the brain of adults after a neurotoxic dose of
TET are insufficient to inhibit ATPase suggesting that inhibition of this enzyme is
not a factor in adult TET neurotoxicity; in the neonate TET brain levels are high
enough to inhibit ATPase and may interfere with mitochondrial function causing
neuronal damage)
34
-------
54. Veronesi, B. and Bondy, S. (1986). Triethyltin-induced neuronal damage in
posmatally exposed rodents. Neurotoxicology, 7: 207-2 16. (TET - acute, 0, 6
mg/kg I?; salt; rat, LE, male, PND5; No TC; DEV; SN; ANAT, BIOCHEM; light
microscopic examination at PND2O indicate TET altered Timm’s, GFAP and
acetyicholinesterase staining patterns in hippocampus and caused reduced whole
brain and hippocampus weights as well as decreased cholinergic receptor binding in
hippocampus; starved controls indicate CNS alterations are not a function of
nutritional deficits; TET may interfere with development of neuronal as well as
myelin elements)
55. Walsh, T. J., Miller, D. B. and Dyer, R. S. (1982). Trimethyltin, a selective limbic
system neurotoxicant, impairs radial-arm maze performance. Neurobehav.
Toxicol. Teratol. 4: 177-183. (TMT CL - acute, 0, 6 mg/kg OR; base; rat, LE,
male, adult; TC; MD; SN; BEHAV, ANAT; rats trained in a radial-arm maze and
then treated with TMT showed gradual development of hyperactivity and persistent
deficits in accuracy suggesting CNS damage induced by TMT interferes with
learning and memory processes; light microscopic examination and quantification
indicated pyramidal cell line length was reduced but this indicator of hippocampal
damage did not account for the behavioral changes)
56. Walsh, T. J., Gallagher, M., Bostock, E. and Dyer, R. S. (1982). Trimethyltin
impairs retention of a passive avoidance task. Neurobehav. Toxicol. Teratol. 4:
163-167. (TMT CL - acute, 0, 5, 6,7 mg/kg OR; base; rat, LE, male, 90 - 120 d &
250 - 300 g; No TC; SN; BEHAV; shorter step-through latencies and freezing
durations during the retention test of a one-trial passive avoidance task, but no
differences in footshock sensitivity, indicate rats treated with TMT have
compromised learning and memory abilities)
research area addressed and primary method employed is in bold type.
ABBREVIATIONS: methods development (MD); environmental and organismic variables (EOV);
developmental neurotoxicity (DEV); specific neumtoxicity (SN); dose-response and exposure scenarios
(DR); conceptual understanding of neurotoxicity (CU); review (REV); time course (TC); oral (OR);
intraperitoneal (IP); intravenous (IV); subcutaneous (SC); triethyltin (TET); trimethyltin (TMT); tributyltin
(TBT); bromide (BR); hydroxide (OH); chloride (CL); oxide (oxide); sulfate (SUL); Long-Evans (LE);
Sprague-Dawley (SD); gestational day (GD); postnatal day (PND); anatomical (ANAT); analytical
(ANALY); behavior (BEHAV); biochemical (BIOCHEM); central nervous system (CNS);
electrophysiology (ELEC); physiology (PHY); teratology (TERATOL); toxicology (TOXICOL); visual
evoked response (VER); day (d); gram (g);
35
------- |