vexEPA
United States
Environmental Protection
Agency
Environmental Monitoring
and Support Laboratory
Las Vegas NE 89114
Research and Development
EPA-600/PS3-80-085 Sept. 1980
Project Summary
Biliary Excretion and Tissue
Distribution of Cadmium-109
Administered to Rats
A.A. Mullen and R.E. Mosley
This report is part of a series of in-
vestigations undertaken to establish
the absorption/excretion character-
istics of various metal pollutants in
order to provide information for selec-
tion of relatively rapid mammalian
tests for estimating exposure. This
study was designed specifically to
ascertain the role of bile in the excre-
tion of cadmium following oral or in-
travenous administration of cadmium-
109 to rats. Results of the study show
that bile concentrates cadmium and
transports it into the gastrointestinal
tract where it may be either reab-
sorbed or excreted in the feces.
Tissue distribution of the cadmium
was also determined in the study.
Regardless of the route of administra-
tion, the liver retained the highest cad-
mium concentration, although kidney
and bone also retained a large percen-
tage of the administered radionuclide.
This publication is a summary of the
complete report, which can be pur-
chased from the National Technical
Information Service.
Introduction
Cadmium is present as a trace metal in
the earth's crust and as an impurity in ores
of other metals. Concentration of ores
and use of cadmium in industrial pro-
cesses have caused cadmium to
become an environmental pollutant
producing a variety of toxic effects.
Because the body appears to lack an
effective mechanism for eliminating cad-
mium, cadmium burden gradually in-
creases with age. In addition, complex in-
teractions that occur between cadmium
and other divalent cations make predic-
tions of intestinal absorption very dif-
ficult.
This study was undertaken to provide
further information on the absorption, ex-
cretion, and tissue distribution of cad-
mium in the rat, in an effort to select
universally available biological monitors,
and to provide a reliable method for quick-
ly estimating potential exposure of critical
segments of a population to a potentially
hazardous pollutant.
Results
The difference in the excretion of cad-
mium in urine and feces was measured in
rats with either ligated or intact bile ducts.
Three days following a single oral-
administration of cadmium-109 plus
stable cadmium chloride, 4 x 10 3 percent
of the dose was excreted in the urine of
rats with intact bile ducts, while 5 x 10 2
percent was excreted in urine of rats with
ligated bile ducts. While 82 percent of the
dose was excreted via the feces of intact
rats, 71 percent was recovered in feces
from rats with ligated bile ducts. The
amount of the dose recovered in tissue
was 13 percent for intact rats and 30 per-
cent for ligated rats.
Following intravenous administration of
cadmium, rats with intact bile ducts ex-
creted about 5 x 10-1 percent of the dose
in urine versus 2 percent for rats with
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Table 1. Average Percent of Cadmium Dose Recovered Per Tissue
Tissue
Oral
Ligated
Non-Ligated
Intravenous
Ligated
Non-Ligated
Liver
Spleen
Kidney
Heart
Brain
Skull
Bone*
1.86 + 0.89
4.65 ± 0.79 x 10-2
0.21 ± 0.08
3.20 ± 0.27 x 10-2
2.20 ± 0.24 x 10-2
4.36 + 0.93 x 10-2
4.23 ± 0.55 x 10-2
1.64 ± 0.67
4.49 ± 0.81 x 10-2
6.88 + 3.58 x 10-2
3.05 ± 0.40 x 10-2
2.01 ± 0.35 x 10-2
3.02 ± 1.01 x 10-2
1.90 ± 0.32 x 10-2
39.3 ± 14.8
4.37 ± 3.51 x 10-1
7.45 ± 1.95
2.96 ± 0.57 x 70-1
2.85 ± 0.76 x 10-2
4.20 ± 1.13x 70-i
2.82 ± 0.22
30.1 ± 10.4
4.60 ± 0.98 x 70-1
7.36 ± 4. 16
2.30 ± 7.52 x 70-1
2. 19 ± 1.50 x 70-i
2.09 ± 7.72x 70-1
3. 16 ± 0. 12
^Estimation based on percentage of body weight assigned to the bone of adult rats as reported by Sikor and Mahlum.
ligated bile ducts. About 8 percent of the
dose was excreted via the feces of rats
with intact bile ducts, compared to only
about 6 x 10-1 percent by ligated rats.
The amount of the dose recovered in the
tissues was 91 and 96 percent respectively
for intact and ligated rats.
As shown in Table 1, the liver, retaining
the highest concentration, appears to be
the organ of primary concern in this
study, although cadmium was also re-
tained in the kidneys and bone.
Conclusions
This investigation clearly demonstrated
that bile plays and important role in the
concentration and transport of cadmium
for subsequent reabsorption or excretion.
Collection of bile from animals endemic to
a potentially polluted area would enable
an investigator to easily determine an ear-
ly increase in biologically available cad-
mium. However, caution must be exer-
cised when attempting to correlate the
amount of cadmium in the bile with the
dose of cadmium received, as dose
threshold effects and possible
synergistic reactions with other
pollutants may affect the kinetics of bile
production.
Authors are EPA employees with the Environmental Monitoring Systems
Laboratory, Las Vegas, NV (see below)
The complete report, entitled "Biliary Excretion and Tissue Distribution of
Cadmium-109 Administered to Rats," {Order No. PB 8021 7995; Cost: $5.00.
subject to change) will be available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
EPA authors can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protect/on Agency
Las Vegas, NV 89114
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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