ACETAMLDE, DIMETHYLCARBAMYL CHLORIDE, AND RELATED  COMPOUNDS
           CARCINOGENICITY AND STRUCTURE-ACTIVITY
       RELATIONSHIPS.  OTHER BIOLOGICAL PROPERTIES.
         METABOLISM.  ENVIRONMENTAL SIGNIFICANCE.
                   David Y. Lai, Ph. D.
                   Yin-tak Woo, Ph. D.,
               Joseph C. Arcos, D. Sc., and
                   Mary F. Argus, Ph.  D.
            Preparation for the Chemical Hazard
             Identification Branch "Current
                   Awareness" Program

-------
                        Table  of  Contents;
            \.

5.2.2.7           Acetamide, Dimethylcarbamyl Chloride and
                  Related Compounds

  5.2.2.7.1       Introduction

  5.2.2.7.2       Physical and Chemical Properties.  Biological
                  Effects.

    5.2.2.7.2.1   Physical and Chemical Properties

    5.2.2.7.2.1   Biological Effects other Than Carcinogenesis

  5.2.2.7.3       Carcinogenicity

  5.2.2.7.4       Metabolism and Mechanisms of Action

  5.2.2.7.5       Environmental Significance

References

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5.2.2.7  Acetamide, Dimethylcarbamyl Chloride, and Related Compounds
     5.2.2.7.1  Introduction.
     This -group of compounds includes amides of simple carboxylic acids, their

N,N-dialkyl derivatives, and related compounds.  The general structure of

these compounds is:
                                            .R'
                                R - C - N^
                                          ""R"
where R, R', and R" are alkyl groups or hydrogen atoms except in dimethyl-

carbamyl chloride, where R is a chlorine atom.  Adipamide is a diamide derived

from adipic acid.  The chemical formulas of acetamide and related compounds,

which have been bioassayed for carcinogenicity, are shown in Table I.


     Early interest in the carcinogenicity of this class of compounds arose

from a chance observation in a routine toxicologic study of acetamide.  In

1955, Dessau and Jackson, while examining the chronic toxic effects of aceta-

mide, discovered a single hepatic tumor in one rat, together with various

hepatic tissue alterations in other animals treated with large doses of aceta-

mide.  The weak carcinogenic activity of acetamide was confirmed in subsequent

studies (1-3).  A number of investigators found acetamide a useful tool for

the study of experimental liver cancer because of its low toxicity and

simplicity of chemical structure (1, 3).


     Because of their homology and/or similarity to acetamide, the structure-

activity relationships of several amides and their substituted derivatives

have been explored (2, 4).  For example, hexaneamide, a higher homolog of

acetamide, has been found to induce malignant lymphomas in mice (3).  Di-

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methylcarbamyl chloride (DMCC), an industrial chemical used as an intermediate




in the manufacture of carbamate pesticides and Pharmaceuticals, is a potent




carcinogen in mice (5, 6), and rats and hamsters (7).  In 1976, the National




Institute for Occupational Safety and Health (NIOSH) had sent a warning to the




industries regarding the potential hazard to workers exposed  to DMCC, despite




the relatively limited quantities of DMCC produced in the United States (8).




In a recent abstract publication, Segal ^_al^. (9) have implied that diethyl-




carbamyl chloride, a close analog of DMCC, is also a carcinogen in rodents.









     5.2.2.7.2  Physical and Chemical Properties,.^. Biological Effects.





     5.2.2.7.2.1  PHYSICAL AND CHEMICAL PROPERTIES.





     The physical and chemical properties of acetamide and related compounds




have been described and discussed by various investigators (10-16).  Some




physical constants of these compounds are presented in Table  I.  In general,




all simple acid amides (except forraamide) are crystalline solids.  Their




boiling points are considerably higher than those of the respective acids.




Lower acid amides such as acetamide are soluble in water.  Solubility tends to




decrease with increasing molecular weight.  N-substitution by methyl or ethyl




group£) lowers the melting point and increases the water solubility of the




compounds.  The N,N-disubstituted amides, dimethyl- and diethylformamide, and




dimethyl- and diethylacetamide, are liquids at room temperature.  The high




dielectric constants, the electron donor properties, and the  ability to form




complexes render these compounds remarkably suitable as solvents for a wide




range of organic and inorganic compounds (15, 16).





     Hydrolysis to the parent carboxylic acids and amines or  ammonia is the




most general reaction of acid amides.  The reaction is accelerated by strong

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                  Table  I.   Chemical  Structures  and  Some  Physical  Properties  of  Acetamide,
                             Dimethylcarbamyl Chloride, and Related Compounds3
Compound
Acetamide

Dimethylcarbamyl
chloride (DMCC)
Dimethylacetamide
Diethylacetamide

Dimethylformamide
Diethylformamide
Formula b.p. (°C)
0
It
CH3-C-NH2 222
0
||
C1-C-N(CH3)2 64
0
II
CH3-C-N(CH3)2 166
0
II
pit _/*_W/' r* U 'N 1 fi O
v»ii» v» ii^ L»_ n._ ) _ J.O £.
0
H-C-N(CH3)2 153
0
II
H-C-N(C H ) 177
Vapor
Pressure Density
(mm Hg) (20°C)
10.0 (105°C) 1.159

— 1.168
9.0 (60°C) 0.937
2.0 (35°C) 0.920

3.7 (25°C) 0.953
1.0 (25°C) 0.908
Solubility
in Water
98 g/100 ml

Hydrolysis
Very high
—

Very highb
Very highb
aData compiled from D.W. Fassett.  In;  Ind. Hyg. Toxicol. (Patty, F.A., ed.), 2nd ed., Interscience, 1963,
 p. 1827; and L.J. Fleckenstein.  In:  Kirk-Othmer Encyclopedia of Chemical Technology, Vol.  2,  2nd ed.,
 1963, p. 66.

bMiscible at any proportion.

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acids or bases.  For instance, acetamide can be converted to acetic acid by




heating with mineral acids or by reaction with nitrous acid.  When heated




either with phosphorus pentoxide or acetic anhydride, acetamide is dehydrated




to yield acetonitrile.  Acetamide can also undergo the Hofmann reaction to




yield monomethylamine.  Reaction of acetamide with alkali metals gives the




corresponding metal derivatives in which the metal is linked to the




nitrogen.  In the presence of hot alkali, acetamide is saponified.  Similar




reactions occur with disubstituted amides under appropriate conditions.





     Dimethylcarbarayl chloride is a colorless liquid prepared by the reaction




of dimethylamine with phosgene.  The compound may be readily hydrolyzed with a




half-life of about 6 minutes at 0°C, yielding dimethylamine, hydrochloric acid




and carbon dixoide (17).  Dimethylcarbamyl chloride is expected to be a




direct-acting acylating agent via its cation (5) which can be stabilized by




the resonance structures:








                     CH.,                    CH3'




                          'N  -  C  =  0     ^       N =  C =  0
     5.2.2.7.2.2  BIOLOGICAL EFFECTS OTHER THAN CARCINOGENESIS





     Toxic Effects.  Acute studies with different animal species show that




acetamide is only slightly toxic; the LDcQ value by parenteral administration




is approximately 10 g/kg in mice and rats (18, 19).  In subacute and chronic




toxicity studies, acetamide did not induce any significant toxic manifestation




in rats and rabbits (18, 19).  Early cellular lesions detected microscopically




were found to be reversible (18).

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     Increase in molecular v/eight and/or N-substitution of the amide with




alkyl groups enhances the toxicity of simple amides (18, 20).  The LD5Q values




of acetamide and,related compounds are given in Table II.  Dimethyl and




diethylformamide, and dimethyl and diethylacetamide all exhibit similar toxic




effects in animals.  They are only moderately toxic when ingested or upon




brief exposure of the skin to the substance (27-29).  Systemic injury can




occur when they are inhaled or absorbed through the skin in large quantities




over a prolonged period of time.  Diethylformamide and diethylacetamide are




potent in inducing cardiovascular effects and inhibit the activities of




convulsants and hypnotic drugs (30, 31).  The clinical symptoms observed in




experimental animals administered dimethylformamide or dimethylacetamide




chronically include hepatic necrosis, weight loss, anorexia, hyperglycemia,




cardiomyopathy, and histopathy in the kidneys, pancreas, spleen, adrenals, and




thymus (27, 32-35).  Epigastric distress, nausea, vomiting, dermal irritation,




abnormal respiratory and hepatic function have also been reported in workers




following accidental dermal and respiratory exposure to these compounds (36-




39).  In addition, alcohol intolerance with flush reaction is a form of




adverse response to dimethylformamide exposure in humans (40, 41); this




"Antabuse effect" is due to the inhibition of liver alcohol dehydrogenase by




dimethylformamide (42).  Because of its cytotoxic activity, dimethylacetamide




has been used as an experimetnal drug for cancer chemotherapy.  Weiss et al.




(43) reported that cancer patients receiving high doses of dimethylacetamide




developed striking hallucinations with predictable regularity.





     Von Hey jet_^l_. (21) have undertaken an extensive toxicological study on




DMCC.  Skin irritation, degeneration of the epidermis, conjunctivitis, and




keratitis were seen in rats and rabbits upon contact with undiluted DMCC on




the skin and eyes.  Inhalation studies in rats showed that almost all animals

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Table II.  Acute Toxicity of Acetamide, Dimethylcarbamyl  Chloride,
                      and  Related  Compounds
Compound
Acetamide '



Dimethylcarbamyl
chloride (DMCC)
n-Hexaneamide
Dimethylacetamide





Diethylacetamide


Dimethylforraamide

.









Diethylfortnamide
Adipamide
Species and Route
Rat, i.p.
Rat, i.v.
Mouse, i.p.
Mouse, i.v.
Rat, oral
Mouse, i.p.
Rat, oral
Rat , oral
Rat, i.v.
Rat, i.p.
Mouse, oral
Mouse, i.v.
Mouse, i.p.
Rabbit, i.v.
Rat, i.p.
Mouse, i.p.
Rat , oral
Rat, i.v.
Rat, i.p.
Mouse, oral
Mouse, i.v.
Mouse, i.p.
Mouse, inhalation
Dog, i.v.
Cat, i.p.
Rabbit, i.v.
Rabbit, i.p.
Guinea pig, i.v.
Rat, i.p.
Mouse, oral
LD50 (g/kg)
10.30
10.00
10.09
8.30
1.17
0.35
1.70
5.09
2.64
3.84
4.62
2.32
4.19
0.80
1.84
1.69
2.80
2.00
1.40
3.75
2.80
0.65
9.40 (2 hr)a
0.47
0.50
1.00
1.00
1.03
1.74
6.00
Reference
(18)
(19)
(18)
(19)
(21)
(21)
(22)
(23)
(23)
(18)
(23)
(24)
(18)
(24)
(18)
(18)
(22)
(22)
(22)
(22)
(24)
(22)
(22)
(26)
(22)
(24)
(22)
(22)
(26)
(22)
aLC5Q (gm/m3)

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died after exposure for 1 to 2 hours to an atmosphere saturated at  20°C with




DMCC.  The chemical caused death by damaging the mucous membrane of  the




respiratory tract followed by difficulty in breathing.  There  is also  report




of eye irritation and liver disturbances in humans exposed to  DMCC  at  the




workplace (21).





     Mutagenic Effects.  Acetamide and DMCC were among the 102 chemicals




selected by the U.S. National Cancer Institute for mutagenicity testing in a




program to determine the extent of correlation between carcinogenesis  and




mutagenesis in a standardized assay system (44).





     Despite its well established hepatocarcinogenic activity, acetamide is




not mutagenic in vitro in various tester strains of Salmonella typhimurium




(45-48), Saccharomyces cerevisiae (49), and Escherichia coli  (46, 48)  tested




in vitro with and without microsomal activation or in host-mediated assay




(50).  Dimethylformamide is inactive in both the Ames test (51) and in the




unscheduled DNA synthesis assay using primary rat liver cell  cultures  (52).




No increase in the number of revertants was observed when testing dimethyl-




acetamide in TA1535 and TA100 tester strains of S_. typhimurium with or without




microsomal activation (53).





     In contrast to the amides, dimethylcarbamyl chloride is  strongly  muta-




genic in a series of microbial strains including _S_. typhimurium TA1535, TA100




(45, 47, 54-56), _E. coli WP-2, WP-2S (46, 55) and_S. cerevisiae D-3 (49).




Diethylcarbamyl chloride is a somewhat weaker mutagen than DMCC and causes




base-pair substitutions as well as deletions in Sj. typhimurium and  J2.  coli




(cited in ref. 57).  Addition of S-9 mix was not required for  mutagenicity in




any of these assays.

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     Teratogenic Effects.  A number of studies have indicated that many acid




amides and their substituted derivatives are embryotoxic and teratogenic.




Acetamide and dimethylacetaoide exhibited weak embryolethal effects when they




were given by gavage to rabbits between the 6th and 18th day following




insemination (58).  Moderate embryo mortality was found with dimethylacetamide




applied to the skin of pregnant rats during the period of fetal organogenesis




(59).  Given to rats subcutanebusly on day 10 to 14 of pregnancy, dimethyl-




acetamide caused fetal resorption and malformations (59-61).  The most sensi-




tive period for the teratogenic effects was found to be around the 10th day of




gestation (60).  Diethylacetamide was reported to have similar teratogenic




activity as dimethylacetamide in the rat (61).  Various embryotropic, gonado-




tropic, and teratogenic effects of dimethylformamide have been repeatedly




demonstrated in mice (62, 63), rats (64-66) and rabbits (58, 59) receiving the




compound by various routes of administration.  These effects include reduced




fertility, increased mortality, biochemical changes in the maternal and fetal




organs, and embryonal malformations.  Regarding humans, Schottek (67) reported




that exposure of pregnant women to dimethylformamide resulted in up to 10-fold




increase in miscarriage.  The compound is believed to penetrate the placental




barrier and affect embryonic development (67, 68).








     5.2.2.7.3  Carcinogenicity.





     Early evidence for the carcinogenicity of acetamide and DMCC have been




reviewed in two IARC monographs (69, 70).  A summary of the carcinogenicity




data of these and related compounds is presented in Table III.





     The first report on the carcinogenic activity of acetamide by Dessau and




Jackson (71) described a hepatocellular adenoma in 1 of the 5 male Rockland




albino rats given oral doses of 4 g/kg acetamide 5 days/week for 205 days.

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            Table III.   Carcinogenicity of Acetamide, Dimethylcarbamyl Chloride
                                   and Related Compounds
Compound
Acetamide





Dimethylcarbamyl
chloride (DMCC)




H ex ane amide

Dimethylacetamide



Dimethylformamide

Species & Strain
Rat, albino,
Wistar, or
Fischer
Mouse, C57B1/6


Mouse, Swiss
Mouse,- Swiss

Mouse, Swiss
Hamster, Syrian golden
Rat, —
Mouse, C57B1/6

Rat , Fischer
Rat, —
Dog, —

Rat, Wistar
Hamster, Syrian golden
Route
oral


oral


topical
s.c.

i.p.
inhalation
inhalation
oral

oral
inhalation
inhalation
or topical
oral -
i.p.
Principal
Organs
Affected
Liver


Liver , hemato-
poietic system,
stomach
Skin, lung
Local sarcoma,
lung
Local sarcoma
Respiratory tract
Respiratory tract
Hematopoietic
tissues
None
None
None

None
None
Reference
(1-3, 71)


(3)


(5, 6)
(5, 6)

(6)
(7)
(7)
(3)

(4)
(32)
(32)

(72)
(73)
Adipamide
Mouse,/'C57B1/6
oral
None
(3)

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Cytological changes related to cell multiplication were also noted in liver




cells of other acetaraide-treated rats.  Later studies from the same laboratory




further substantiated the hepatocarcinogenic activity of acetamide (1).  In




one experiment, fifty 1-raonth-old male Wistar rats were administered 5%




acetamide continuously in the diet.  Four of the 48 rats treated for 38-52




weeks developed trabecular carcinomas and adenocarcinomas of the liver, with




metastases in the lung.  No tumors were noted in the 50 controls.  In another




experiment, groups of 25 male Wistar rats were continuously fed a diet




containing 0, 1.25, 2.5, or 5.0% acetamide for 1 year.  Liver tumors, some




with invasive growth and distant metastases, were found in 4/24, 6/22, and




1/18 rats treated with low, medium, and high dose levels of acetamide, respec-




tively.  None of the 25 control animals developed tumors.  When 5% acetamide




was fed in the diet to 99 male Wistar rats (and 2 rats were returned to normal




diet weekly), liver tumors were seen in 22/81 rats treated for 14-40 weeks.




The adenocarcinomas observed in the rats were remarkably similar histo-




logically to human cholangiocellular carcinoma.





     These observations were later confirmed by Weisburger et_ al^.  (2) who




found that 7 of 16 male Wistar rats fed 0.25% acetamide in the diet for 12




months developed malignant liver tumors after a 15-month total observational




period.  Moreover, Fleischman et_ ai. (3) described neoplastic nodules and




hepatocellular carcinomas in rats of both sexes receiving 2.36% acetamide in




the diet for 12 months; the tumor incidence was greater in males (41/47) than




in females (33/48).  The latter study suggests that the occurrence of mixed




cell foci and focal fatty changes may represent histopathological markers for




the carcinogenicity of acetamide in the rat.





     Additional target organs for acetamide carcinogenesis were seen in




mice.  The study of Fleischman et al. (3) showed that in male mice, there was

-------
a dose-dependent increase in the incidence of malignant lyaphomas.  These




tumors occurred in 7/50 (14%) and 7/46 (15%) of male mice given 1.18% and




2.36% acetamide,^respectively, in the diet for 12 months, compared to 0/95 of




the controls.  A 5/50 incidence of papillomas in the stomach was also detected.




in male mice receiving the 1.18% dietary level; however, this was considered




to be of questionable significance since it was not observed in male mice




receiving the 2.36% dietary level or in any female mice.





     Consistent with the negative mutagenic effects of dlmethylacetamide and




dimethylformamide, a variety of studies failed to demonstrate any carcinogenic




activity of these two compounds.  In a chronic dermal study by Horn (32), 0.1




or 0.32 ml/kg dimethylacetamide was applied to the skin of 2 dogs of an




unspecified strain daily (at each dose level) for 6 months.  No neoplastic




lesions were observed in the treated animals at the end of exposure.  In the




study of Hadidian £t_ jil_. (4) there was no difference in the incidence of




neoplastic lesions which occurred in both the control rats and those given




0.1, 3, 10, or 20 mg dimethylacetamide by gavage daily, 5 days/week for a




total of 260 doses.  Also, no tumors attributable to dimethylacetamide




exposure could be detected during a chronic inhalation study in which 2 dogs




and 20 rats were exposed to 40, 64.4, 103, or 195 ppm of the compounds for a




duration of 6 months on a 6 hour/day, 5 days/week basis (32).





     Dimethylformamide has been used as a solvent control in carcinogenicity




studies on aflatoxin.  No tumors were found in 19 Wistar rats given a single




intragastric dose of 0.1 ml of dimethylformamide and observed for 13 to 34




months (72).  Neoplastic lesions were observed neither in 10 Syrian hamsters




receiving 0.1 ml 50% solution of dimethylformamide weekly for 6-8.5 months by




intraperitoneal injection (73).  The lack of carcinogenicity of dimethyl-




formamide is further supported by the studies of Purchase et al.  (51).  These






                                       8

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investigators found dimethylforaamide negative in six standard short-term

tests for carcinogenicity, while dimethylcarbamyl chloride was positive in

four of these assays.


     The testing of hexaneamide and adipamide
                           0                    00
                           II                    II             It
                         - C  - NH        HN - C  -  (CH    -  C  -
                 Hexaneamide                      Adipamide



for carcinogenicity was carried out in Fischer 344 rats and C57B1/6 mice by


Fleischman et_ jil_. (3).  Administration of hexaneamide at dietary levels of


1.0% and 1.5% for 12 months did not induce significant carcinogenic effects in


rats of either sex, or in female mice.  However, 6/35 and 6/39 male mice


receiving 1.0% and 1.5% hexaneamide in the diet, respectively, developed


malignant lymphomas which were described as grossly and microscopically


resembling those induced by acetamide.  None of the 95 matched controls bore

this type of tumors.  Adipamide was given to 50 rats and 50 mice of both sexes


in the diet (2.4% and 5.8% in rats; 1.6% and 2.4% in mice) for 12 months.

Five of 49 male rats which survived the high dose developed the type of liver


tumor induced by acetamide.  All the 5 rats bearing neoplasms were housed in


the same cage.  Because of the unusual distribution of the affected animals,

the results were interpreted by the investigators to be inconclusive.  No


significant incidences of tumors were observed in female rats or mice of both


sexes ingesting adipamide at high or low dose.


     Dimethylcarbamyl chloride is a potent carcinogen in mice when applied to

the skin or injected subcutaneously.  In 1972 Van Duuren et_ £l_. (5) observed a


60% incidence of skin tumors (46% papillomas and 22% carcinomas) and a 4%

-------
incidence of papillary tumors of the lung in 50 female ICR/Ha Swiss mice




following application of 2 mg DMCC to the skin three times weekly for 55




weeks.  Subcutaneous injections of 5 mg DMCC in 0.05 ml tricaprylin weekly to




50 female mice of the same strain weekly for 26 weeks resulted in a 72%




incidence of local sarcomas and an 8% incidence of papillary tumors of the




lung (5).  No      tumors were noted in the solvent control group or in the




untreated groups.





     When DMCC (1 mg in 0.05 ml tricaprylin) was applied to mice weekly by




intraperitoneal injection for 65 weeks, 8/30 treated mice developed local




sarcomas compared with 1/30 control mice given the solvent alone and 0/100




untreated mice (6).  Fourteen of 20 DMCC-treated mice, 10 of 30 control mice




given tricaprylin alone, and 29 of 100 untreated mice also developed papillary




tumors of the lung.





     The findings of an Inhalation study by Sellakumar _££_£!_• (7) using




hamsters and rats further emphasize the potent carcinogenic activity of




DMCC.  In this study, male Syrian golden hamsters and rats of an unspecified




strain were exposed to 1 ppm DMCC 6 hours/day, 5 days/week for the lifetime of




the animals.  The rats were highly sensitive to the compound; 94 of 98 treated




animals developed squamous cell carcinomas of the nasal tract 196-348 days




after the onset of the exposure (57; cited in ref. 74).  Although hamsters are




notably resistant to other pulmonary carcinogens (75, 76), 50 of 99 DMCC-




exposed hamsters developed tumors in the nasal cavity between day 406 and day




770 of the exposure.  No tumors were observed in the 120 untreated or the 50




matched air-exposed controls.





     There has been no report on the carcinogenicity study of diethylcarbamyl




chloride.  However, the similarities in structure and in mutagenic action
                                      10

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between DMCC and diethylcarbamyl chloride have led Van Duuren to the conclu-




sion that diethylcarbamyl chloride has a high probability of being a




carcinogen (57).- A recent communication by Segal £t_ jil_. (9) implies that




diethylcarbamyl chloride is a rodent carcinogen, with an activity somewhat




lower than DMCC.








     5.2.2.7«4  Metabolism and Mechanisms of Action.
     Metabolism studies in animals showed that 70% of the acetamide admini-




stered is excreted unchanged in the urine over a 4-day period (77).  However,




a small amount of the compound is believed to undergo hydrolysis or enzymatic




deanination to yield acetate and ammonium ion (2).  The mechanism of carcino-




genic action of the compound, despite (or because of) its structural




simplicity, is still unknown.  Weisburger et al^. (2) have shown that arginine




glutamate, an agent which counteracts the toxicity of ammonia (78), has a




protective effect against the hepatocarcinogenicity of acetamide in rats.  The




finding led these investigators to the hypothesis that acetamide may be




carcinogenic toward the liver because of chronic intracellular liberation of




ammonia.  That dimethylformamide and dimethylacetamide, with their amide




hydrogen atoms replaced by methyl groups, are not carcinogenic (Section




5.2.2.6.3) appeared to be in line with this hypothesis.  However, the level of




urinary and serum ammonia nitrogen in rats fed acetamide after 4 weeks or 12




months was found not different from that observed in controls (2).  Further-




more, feeding of ammonium citrate to rats at dose levels equimolar to a




carcinogenic dose of acetamide for 12 months did not elicit any neoplastic




lesion in the liver (2).  Fleischman ^£_al^. (3) suggested that acetamide and




hexaneamide might cause lymphomas in mice probably by interaction with latent




viruses or endogeneous hormones.
                                      11

-------
     Amides are generally regarded as hydrogen-bonding agents which modify the


 tertiary structure of macromolecules.  Since certain chemical carcinogens


 alter the conformation of proteins and nucleic acids, it has been hypothesized


 that carcinogenesis may involve small selective conformational changes or


 drastic denaturation of certain biological macromolecules essential to the


 growth and control of target cells (79, 80).  In vitro studies have indeed


 demonstrated that ace t amide brings about the denaturation of proteins (80) as


 well as the formation of hydrogen-bonded associations with nucleic acids (81,


 82).  Autoradiographic studies by Kajijat^^. (83) showed that ^H-acetamide
                                                                   3
incorporates into the nuclei of Ehrlich ascites tumor cells.  Like  H-thymidine,


the incorporation of  H-acetamide into nuclei was inhibited by mitomycin C,


indicating that the incorporation of acetamide is in close connection with DNA


synthesis.  Based on the observations that acetamide inhibits the incorpora-

        o
tion of  H-thymidine into the nucleotide pool and into DNA, as well as the

                 00
incorporation of J^P into the phospholipids of cultured human cells, Keysary


and Kohn (84) suggested that acetamide may- alter the cell membrane.  The


epigenetic theory for acetamide carcinogenesis would provide an explanation


for the negative results in the mutagenicity tests of acetamide (Section


5.2.2.7.2.2).  The relationships between effect on DNA synthesis and cell


membrane effects, and between denaturation of cellular macromolecules and


carcinogenesis by acetanide remain to be investigated.
                                      12

-------
     It has already been pointed out that DMCC is a direct-acting acylating

carcinogen* via the cation (CH3)2N-C=0» which is highly reactive toward

nucleophiles (5).  Recently, the formation of 0 -dimethylcarbamyldeoxy-

guanosine following in vitro reaction between DMCC and calf thymus DNA has

been shown (9).  Similarly, 0 -diethylcarbamyldeoxyguanosine was detected in

the nucleoside hydrolysate following in vitro reaction of diethylcarbamyl

chloride and DNA (9).

     The metabolism of dimethylformamide and dimethylacetamide has been

studied both in vitro and in vivo by Barnes and coworkers (85, 86).  In vitro

studies with rat liver honogenates have indicated that demethylation is the

metabolic pathway for these amides.  Demethylation was enhanced when the rats

were pretreated with phenobarbital, presumably because of the induction of the

N-demethylase in the microsomes.  N-Monomethylformamide and N-monomethylaceta-

mide have been isolated and identified as the major urinary metabolites in

rats administered dimethylformamide and dimethylacetamide, respectively.

These metabolites were also detected in the urine of humans exposed to

dimethylformamide and dimethylacetamide (88, 89).



     5.2.2.7.5  Environmental Significance.


     Acetamide does not occur naturally.  However, is has been reported that

"over-oxidized," spoiled wine contains acetamide (cited in ref. 69).
*The dimethyl carbamyl cation is an example of a recently emerging  new  class
 of carcinogens, the direct-acting acylating agents.  The fact  that alkylating,
 arylating, and acylating agents can all function as carcinogens  indicate  that
 the chemical nature of the xenobiotic molecular moieties attached  to key
 informational macromolecules is probably immaterial as long as these attach-
 ments interfere with the biosynthetic template function of these macromole-
 cules (87).  Direct-acting acylating agents will be further discussed  in
 Appendix I of this volume.


                                      13

-------
Acetamide has recently been identified as a metabolite of netronidazole, a




drug used in the treatment of trichomonal vaginitis and various forms of




amebiasis (90, 91).  Metronidazole was found by Rustia and Shubik (92) to




induce lung tumors and malignant lymphomas by oral administration to Swiss




mice.  However, the carcinogenicity of metronidazole must be attributed to its




structural relationship to the 5-nitrofuran carcinogens (see Section




5.1.2.4.1.3, Vol. IIB) rather than to the metabolic release of acetamide.





     Since acetamide has numerous industrial uses, human exposure to the




compound also occurs in the workplace.  Acetamide has been produced commer-




cially in the United States since 1921.  In 1978, about 228 metric tons of




acetamide was produced (14).  It is widely used as solvent, solubilizer,




plasticizer, stabilizer, wetting agent, and antacid in the lacquer, explo-




sives, and cosmetics industries (11, 14).  In addition, it has been reported




to be employed in cryoscopy, in soldering, and in the synthesis of other




organic chemicals, insecticides, and hypnotics (11, 14).  Because of its low




acute toxicity and the lack of awareness of 'its potential chronic effects,




usual handling and use of acetamide were considered in the past to represent




no significant hazard.





     Acetamide has high water solubility and low vapor pressure.  Thus, should




it be released in the environment, it will readily enter the soil and the




water table.  However, unless large amounts are involved, it will not persist




and bioaccumulate.  Biological tests with bacteria, algae, and fish indicate




that very high levels of acetamide are tolerated (93).





     Dimethylcarbamyl chloride is not in extensive use and is produced only in




limited quantities in the United States.  In 1975 only about 3,000 pounds of




the compound was manufactured for the synthesis of certain carbamate pesti-
                                      14

-------
cides and drugs for the treatment of myasthenia gravis (8).  Less than 200




persons were estimated to be occupationally exposed to DMCC (8).  Diethylcar-




bamyl chloride, on the other hand, was reported to be in more extensive use in




the United' States (57).  The compound is particularly important in the produc-




tion of a veterinary antifilarial drug, diethylcarbamazine citrate (57).




Because of the carcinogenic properties of DMCC and diethylcarbamyl chloride,




industries in the United States have been alerted to the potential hazards




involved in handling these chemicals.  In the air of a manufacturing plant in




the Federal Republic of Germany (cited in ref. 70), concentrations of up to




1.5 ppm DMCC have been reported.  However, no cancer deaths or indications of




lung cancer were found in an investigation of 65 DMCC workers and 42 ex-




workers aged 17-65 and exposed for periods from 6 months to 12 years (cited in




ref. 70).





     Little information is available on the environmental occurrence or fate




of DMCC and diethylcarbamyl chloride.  Munn (94) pointed out that DMCC is much




less volatile than bis(chloromethyl)ether, a potent human carcinogen known to




cause respiratory cancers.  Since DMCC is rapidly hydrolyzed in water with a




half-life of about 6 minutes at 0°C (17), the compound will not persist or




bioaccumulate in the aquatic environment.
REFERENCES TO SECTION 5.2.2.7









1.   Jackson, B. and Dessau, F.I.:  Lab. Invest.  10, 909 (1961).




2.   Weisburger, J.M., Yamamoto, R.S., Glass, R.M. and Frankel, H.H:  Toxicol,




     Appl. Pharmacol. 14, 163 (1969).
                                      15

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3.   Fleischman, R.W., Baker, J.R., Hagopian, M., Wade, G.G., Hayden, D.W.,




     Smith, E.R., Weisburger, J.H., and Weisburger, E.K.:  J. Environ. Pathol.




     Toxicol. _3> l'*9 (1980).



4.   Hadidian, Z., Fredrickson, T.N., Weisburger, E.K., Weisburger, J.H.,




     Glass, R.M. and Mantel, N.:  J. Nat. Cancer Inst. 41, 985 (1968).




5.   Van Duuren, B.L., Goldschmidt, B.M., Katz, C. and Seidman, I.:  J. Nat.




     Cancer Inst. j£, 1539 (1972).




6.   Van Duuren, B.L., Goldschmidt, B.M., Katz, C., Seidman, I. and Paul,




     J.S.:  J. Nat. Cancer Inst. 53, 695 (1974).




7.   Sellakumar, A.R., Laskin, S., Kuschner, M., Rusch, G., Katz, G.V.,




     Snyder, C.A. and Albert, R.E.:  J. Environ. Pathol. Toxicol. _4_, 107




     (1980).




8.   Anonymous:  American Industrial Hygiene Association:  Am. Ind. Hyg.




     Assoc. J. 37^, 370 (1976).




9.   Segal, A., Mate, U., Solomon, J.J. and Van Duuren, B.L.:  Proc. Am.




     Assoc. Cancer Res. 22, 84 (1981).




10.  Fleckenstein, L.J.:  In;  Kirk-Othmer Encyclopedia of Chemical




     Technology, Vol. 2, 2nd Ed., 1963, p. 66-72.




11.  Lurie, A.P.:  In;  Kirk-Othmer Encyclopedia of Chemical Technology, Vol.




     2, 2nd Ed., 1963, p. 142-145.




12.  Hubinger, D.C.:  In;  Kirk-Othmer Encyclopedia of Chemical Technology,




     Vol. 2, 2nd Ed., 1963, p. 145-148.




13.  Louderback, H.:  In;  Kirk-Othmer Encyclopedia of Chemical Technology,




     Vol. 10, 2nd Ed., 1963, p. 109-114.




14.  Moretti, T.A.:  In;  Kirk-Othmer Encyclopedia of Chemical Technology,




     Vol. 11, 3rd ed., 1978, p. 148-151.
                                      16

-------
15.  Eberling, C.L.:  In;  Kirk-Othmer Encyclopedia of Chemical Technology,




     Vol. 11, 3rd ed., 1978, p. 263-268.




16.  Siegle, J.C.:  In:  Kirk-Othmer Encyclopedia of Chemical Technology, Vol.




     1, 3rd Ed., 1978, p. 167-171.




17.  Queen, A.:  Canad. J. Chem. 45, 1619 (1967).




18.  Caujolle, F., Chanh, P.H., Dat-Xuong, N. and Azum-Gelade, M.C.:




     Arzneim.-Forsch. 20, 1242 (1970).




19.  Hashimoto, Y., Makita, T., Mori, T., Nishibe, T. and Noguchi, T.:  Oyo




     Yakuri. _4, 451 (1970).




20.  Sherman, G.P., Gatlin, L. and DeLuca, P.P.:  Drug Dev. Ind. Pharm. _4, 485




     (1978).




21.  Von Hey, W., Thiess, A.M. and Zeller, H.:  Zbl. Arbeitsmed. 24,  71




     (1974).




22.  NIOSH:  In;  "Registry of Toxic Effects of Chemical Substances," National




     Institute for Occupational Safety and Health, Cincinnati, Ohio,  1979.




23.  Bartsch, W., Sponer, G., Dietmann, K. and Fuchs, G.:  Arzneim.-Forsch.




     _26, 1581 (1976).




24.  Wiles, J.S. and Narcisse, J.J. Jr.:  Am. Indust. Hyg. Assoc. J.  32, 539




     (1971).




25.  Kutzsche, A.:  Arzneim.-Forsch. 15, 618 (1965).




26.  Heath, D.F. and Magee, P.N.:  Brit. J. Ind. Med. 19, 276 (1962).




27.  Massmann, W.:  Brit. J. Ind. Med. 13, 51 (1956).




28.  Weiss, L.R. and Orzel, R.A.:  Toxicol. Appl. Pharmacol. 11, 546  (1967).




29.  Kafyan, V.B.:  Zh. Eksp. Bain. Med. 11, 39 (1971).




30.  Chanh, P.-H., Azum-Gelade, M.C., Nguyen-Van-Bac and Nguyen-Dat-Xuong:




     Therapie 27, 873 (1972).
                                      17

-------
31.  Budden, R., Kiuhl, U.G. and Buschinann, G.:  Arzneim.-Forsch.  28, 1571




     (1978).




32.  Horn, H.J.; v Toxicol. Appl. Pharmacol. 3, 12 (1961).




33.  Clayton, J.W. Jr., Barnes, J.R., Hood, D.B. and Schepers, G.W.:  Am.  Ind.




     Hyg. Assoc. J. 24, 144 (1963).




34.  Surges, R.A., Blackburn, K.J. and Spilker, B.A.:  Life  Sci.  8, 1325




     (1969).




35.  Grant, A.M.:  Toxicol. Letters  3, 259 (1979).




36.  Martelli, D.:  Med. Lavoro 51.  123 (1960).




37.  Corsi, G.C.:  Med. Lavoro 62, 28 (1971).




38.  Potter, H.P.:  Arch. Environ. Hlth. 27, 340 (1973).




39.  Chary, S.:  Lancet 11, 356 (1974).




40.  Wink, A.:  Ann. Occup. Hyg. 15, 211 (1972).




41.  Chlvers, C.P.:  Lancet 1, 331 (1978).




42.  Weiss, A.J., Mancall, E.L., Koltes, J.A., White, J.C. and Jackson,




     L.G.:  Science 136, 151 (1962).




43.  Sharkawi, M.:   Toxicol. Letters 4, 493 (1979).




44.  Poirier, L.A. and Weisburger, E.K.:  J. Nat. Cancer Inst. 62,  833  (1979).




45.  McCann, J., Choi, E., Yamasaki, E. and Ames, B.N.:  Proc. Nat. Acad.  Sci,




     U.S. 72, 5135 (1975).




46.  Rosenkranz, H.S. and Poirier, L.A.:  J. Nat. Cancer Inst. 62,  873  (1979),




47.  Simmon, V.F.:   J. Nat. Cancer Inst. 62, 893 (1979).




48.  McMahon, R.E., CLine, J.C. and  Thompson, C.A.:  Cancer  Res.  39, 682




     (1979).




49.  Simmon, V.F.:   J. Nat. Cancer Inst. 62, 901 (1979).




50.  Simmon, V.F.,  Rosenkranz, H.S., Zeiger, E. and Poirier, L.A.:  J.  Nat.




     Cancer Inst. 62, 911 (1979).
                                      18

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51.  Purchase, I.F.H., Longstaff, E., Ashby, J.A., Styles, J.A., Anderson, D.,


     Lefevre, P.A. and Westwood, F.R.:  Nature 264, 624 (1976).
                 ^

52.  Williams, G.H.:  Cancer Res. 37, 1845 (1977).


53.  Hedenstedt, A.:  Mutation Res. 53. 198 (1978).


54.  McCann, J., Spingarn, N.E., Kobori, J. and Ames, B.N.:  Proc. Natl. Acad.


     Sci. U.S. 72, 979 (1975).


55.  Mukai, F. and Hawryluk, I.:  Mutation Res. 20, 228 (1973).


56.  Anderson, D. and Styles, J.A.:  Br. J. Cancer, 37, 924 (1978).


57.  Nelson, N.:  In;  "Origins of Human Cancer," (Hiatt, H.H., Watson, J.D.,


     Winsten, J.A., eds.), Book A, Cold Spring Harbor Lab., p. 115 (1977).


58.  Merkle, J. and Zeller, H.:  Arzneim.-Forsch. 30, 1557 (1980).
                                                                           I

59.  Stula, E.F. and Krauss, W.C.:  Toxicol. Appl. Pharmacol.  41, 35 (1977).


60.  Anderson, I. and Morse, L.M.:  Exp. Mol. Pathol. 5, 134 (1966).


61.  von Kreybig, T., Preussmann, R. and von Kreybig, I.:  Arzneim.-Forsch.


     _19_, 1073 (1969).


62.  Scheufler, H. and Freye, H.A.:  Dtsch. Gesundheitswes. 30, 455 (1975).


63.  Scheufler, H.:  Biol. Rundsch. 14, 227 (1976).


64.  Sheveleva, G.A. and Osina, S.A.:  Toksikol. Nov. Prom. Khim. Veshchestv.


     13., 75 (1973).


65.  Gofmekler, V.A.:  Gig. Sanit. 39, 7 (1974).


66.  Sheveleva, G.A., Strekalova, E.E. and Chirkova, E.M.:  Toksikol. Nov.


     Prom. Khim. Veshchestv. 15, 145 (1979).


67.  Schottek, W.:  Vop. Gig. Normirovaniya Izuch. Otdalennykh Posledstvii


     Vozdeistviya prom. Veshchestv., p. 119 (1972).


68.  Sheveleva, G.A., Sivochalova, O.V., Osina, S.A. and Sal'nikova, L.S.:


     Akush. Ginekol. (Moscow) 5, 44 (1977).
                                      19

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 69.   IARC:   International Agency for Research on Cancer Monograph  7, 197




      (1974).




 70.   IARC:   International Agency for Research on Cancer Monograph  12,  77




      (1976,).




 71.   Dessau, F.I. and Jackson, B.:  Lab.  Invest. 4, 387 (1955).




 72.   Carnaghan, R.B.A.:  Brit. J. Cancer  21, 811 (1967).




 73.   Herrold, K.McD.:  Brit. J. Cancer  23, 655 (1969).




 74.   Van Duuren, B.L.:  J. Environ. Pathol. Toxicol. _3, 11  (1980).




 75.   Stenback, F.:  J. Nat. Cancer Inst.  50, 895 (1973).




 76.   Sellakumar, A. and Shubik P.:  J.  Nat. Cancer Inst. 53, 1713  (1974).




 77.   Williams, R.T.:  In;  "Detoxication  Mechanisms," 2nd ed.  Wiley,  New  York




      (1959).




 78.   Greenstein, J.P., Winitz, M., Gullino, P., Birnbaum, S.M. and Otey,




      M.C.:  Arch. Biochem. Biophys. 64, 342 (1956).




 79.   Rondoni, P.:  In;  "Advances in Cancer Research," (Greenstein, J.P. and




      Haddow, A., eds.), Vol. 3, p. 171, Academic Press, New York (1955).




 80.  Argus, M.F., Arcos, J.C., Mathison,  J.H. Alam, A. and Bemis,  J.A.:




     Arzneim.-Forsch. 16, 740 (1966).




 81.   Lancelot, G. and Helene, C.:  Nucleic Acids Res. 6, 1063  (1979)..




 82.  Slonitsky, S.V., Maevsky, A.A., Mantulenko, V.B. and Frisman,  E.V.:   Mol.




     Biol. 14_, 753 (1980).




 83.  Kaji, S., Onchi, M. and Michinomae,  M.:  Japan J. Genetics 51, 53 (1976).




84.  Keysary, A. and Kohn, A.:  Chem.-Biol. Interact. 2, 381 (1970).




85.  Barnes, J.R. and Ranta, K.E.:  Toxicol. Appl. Pharmacol.  23,  271  (1972).




86.  Barnes, J.R. and Henry, N.W.:   Am. Ind. Hyg. Assoc. J. 35, 84 (1974).




87.  Arcos, J.C.:.  J. Environ. Pathol.  Toxicol. 1, 433 (1978).
                                      20

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88.  Maxfield, M.E., Barnes, J.R., Azar, A. and Trochimowicz, H.T.:  J. Occup.




     Med. JL7_, 506 (1975).




89.  Krivanek, N.D., McLaughlin, M. and Fayerweather, W.E.:  J. Occup. Med.




     ^0, 179 (1978).




90.  Koch, R.L., Crystal, E.J.T., Beaulieu, B.B. Jr. and Goldman, P.;




     Biochem. Pharmacol. 28, 3611 (1979).




91.  Schwartz, D.E., Jordon, J.-C., Vetter, W. and Oesterhelt, G:  Xenobiotica




     ^, 571 (1979).




92.  Rustla, M. and Shubik, P.:  J. Nat. Cancer Inst. 48, 721 (1972).




93.  Verschueren, K.:  In;  "Handbook of Environmental Data on Organic




     Chemicals," Van Nostrand Reinhold Co., New York, p. 59 (1977).




94.  Munn, A.:  Br. J. Cancer 32, 261 (1975).
                                      21

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Notes Added After Completion of Section 5.2.2.7



     DimethyIformamide was reported in 1979 to induce chromosomal aberrations


in human lymphocytes in vitro (1).  However, a more complete study using


various test systems did not confirm the genotoxicity of dimethylformamide


(2).



     In addition to 0 -dimethylcarbamyldeoxyguanosine, 6-dimethylamino-2'-


deoxyguanosine and 4-dimethylaraino-thymidine are also formed in the in vitro


reaction of dimethylcarbamyl chloride with calf thymus DNA (3).

                        0
                        II
     Acrylamide (CH =CH-C-NH«), a chemical widely used in the synthesis of


polymers, bears a structural resemblance to acetamide with respect to the acid


amide group, and to two other carcinogens, vinyl carbamate (see Section


5.2.1.6 of Vol. IIIA) and acrylonitrile (see Section 5.2.1.7.2 of Vol. IIIA)


with respect to the carbon-carbon double bond.  Like acetamide, acrylamide


does not produce point mutations in Salmonella typhimurium (4).  However, it


induces high frequency of chromosomal aberrations in bone marrow and germ


cells of mice (5).  In 1984, acrylamide was shown to have tumor initiator


activity in the skin of Sencar mice, either by topical application or by


systemic routes of administration.  In addition, the compound induces lung


adenomas in strain A/J mice after oral or intraperitoneal administration


(4).  These findings indicate that acrylamide possesses carcinogenic proper-


ties similar to vinyl carbamate and its postulated parent compound,  ethyl


carbamate (see Section 5.2.1.6 of Vol. IIIA).   In fact, acrylamide is as


potent as ethyl carbamate in the initiation of mouse skin tumors (4).  The


mechanisms of tumorigenic action of acrylamide is unknown.  It is possible


that, acrylamide, vinyl carbamate and acrylonitrile all act via similar


mechanisms by virtue of the carbon-carbon double bond in their molecules.


Acrylamide has been shown to alkylate proteins at the sulfhydryl group (6).

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References for Section 5.2.2.7 Update









  1.  Koudela, K.,  and Spazier, K.:   Cesk. Hyg. 24, 432 (1979).




  2.  Antoine, J.L.,  Arany,  J., Leonard, A., Henrotte,  J., Jenar-Dubuisson,




      G., and Decat,  G.:   Toxicology 26, 207 (1983).




  3.  Segal A.,  Solomon,  J.J., Mate, U., and van Duuren,  B.L.:  Chem.-Biol.




      Interact.  40, 209 (1982).




  4.  Bull, R.J., Robinson,  M., Laurie, R.D., Stoner,  G.D., Greisiger, E.,




      Meier,  J.R.,  and Stober, J. :  Cancer Res. 44, 107 (1984).




  5.  Shiraishi,  Y.:   Mutation Res.  57. 313 (1978).




  6.  Hashimoto,  K.,  and  Aldridge, W.N.:  Biochem.  Pharmacol.  19,  2591 (1970),

-------