Mutagen agents may increase the genetic load of human populations by inducing heritable diseases and cancer. The most effective way of protection is prevention: detection of the mutagenic agents and the regulation of their use. The harm occurred can be visualized by mutational monitoring and epidemiology. The harmful effects of the induced mutations may be reduced to a level accepted by the society with suitable approach and methods. The role of physicians is especially important to fulfil this task.
Using an improved microculture method, we investigated how the patterns of persistence of urethane-induced SCEs in lymphocytes differ among individuals and strains of mice (the ddY and C57BL strains), and we attempted to speculate on their relationship to carcinogen susceptibility. After a single intraperitoneal (i.p.) injection of 900 mg/kg of body weight of urethane into ten female mice each for the two strains, blood samples for the SCE analysis were collected from the tail vein at ten times during the 180 posttreatment days for each individual. Immediately after the treatment, SCE values increased to about three to four times the spontaneous values in all of the animals tested and then fell gradually. (The difference from spontaneous values was statistically significant until 120 days after the treatment.) Even after 180 days, however, some "outlier" cells with exceptionally high SCEs (greater than 20) persisted. Although there was some difference in average SCEs between the ddY and C57BL strains, the magnitude of the difference was too small to account for the difference between the strains in the incidence of urethane-induced malignancy. Also, when autopsy data at the 200th posttreatment day were matched individually with the data of SCE values within each strain, it was difficult to predict the individual risk of the occurrence of lung adenoma or other tumors from the relative difference in SCE values.
Extract of particulate matter (EPM) from gasoline engine exhaust has been investigated for cytotoxic and genotoxic effects in the concentration range 0.16-10 micrograms/ml by means of short-term bioassays using mammalian cell culture systems. Cytotoxicity is demonstrated by a strong dose-dependent reduction of cloning efficiency after treatment of V79 cells with EPM. Employing the dye exclusion test with erythrosin B, no considerable loss of cell viability was observed. Using the same cell system, EPM revealed a highly increased number of aberrant mitoses, whereby the occurrence of C mitoses and metaphases with chromosome clusters was especially pronounced. This effect led to mitotic arrest as shown by a highly increased mitotic index at 5 and 10 micrograms/ml EPM. The results indicate disturbances of the mitotic spindle in a way similar to the known spindle poison colcemid. As a consequence of spindle disturbances, EPM produced numerical chromosome alterations such as aneuploidy and polyploidy. Cytogenetic analyses using human lymphocyte cultures treated with EPM revealed a slight increase of chromosomal aberrations at 10 micrograms/ml and a dose-dependent induction of sister chromatid exchanges in the range 2.5-10 micrograms/ml. At least, EPM showed a dose-dependent increase in the cell transformation assay using SV 40-infected Syrian hamster kidney cultures. The great variety of cytotoxic and genotoxic effects found with EPM suggests a potential health hazard to human populations exposed to gasoline engine exhaust. The possible contribution to cytotoxic and genotoxic activity by organolead compounds derived from antiknock additives is discussed.
The rat liver carcinogen methapyrilene is shown to be a selective mutagen to strain TA1535 of Salmonella typhimurium when tested in the absence of S9 mix and using the standard plate-incorporation assay protocol. The activity observed was weak but was reproducible for a range of samples on many occasions of test and was not due to impurities. These data contrast with six earlier reports of the inactivity of this chemical in the Salmonella mutation assay.
The incidence of sister chromatid exchange (SCE) was investigated in the lymphocytes of control women, pregnant women, and women using oral contraceptives after culture at 37 degrees C and 40 degrees C. At 37 degrees C, the mean frequency of SCE (MEAN +/- S.E.) was found to be 7.91 +/- 0.30 in pregnant women and 8.53 +/- 0.29 in oral contraceptive users which were significantly higher than the SCE value of 5.56 +/- 0.21 found in control women. Increase in growth temperature to 40 degrees C elevated the SCE frequency to 11.86 +/- 0.44 in pregnant women, 12.76 +/- 0.46 in oral contraceptive users and 7.24 +/- 0.26 in control women. These data indicate that there is a differential induction of SCEs following increased cell culture temperature in the lymphocytes of pregnant women and oral contraceptive users, compared with control women.
Environmental MutagenesisVolume 12, Issue 3 p. 343-344 Book Review “Animal alternatives for research alternatives to animal use in research, testing, and education,” Office of technology assessment, congress of the united states. New York: Marcel Dekker, Inc., 1988, 441 pp., $59.75 James M. Gentile, James M. Gentile Biology Department Hope College Holland, MichiganSearch for more papers by this author James M. Gentile, James M. Gentile Biology Department Hope College Holland, MichiganSearch for more papers by this author First published: 1988 https://doi.org/10.1002/em.2860120309AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue31988Pages 343-344 RelatedInformation
Environmental MutagenesisVolume 12, Issue 2 p. 269-270 Book Review Genetic toxicology: A textbook revisited “principles of genetic toxicology, second Edition,” D. Brusick, New York: Plenum Press, 1987, 284 pp., $35.00 James M. Gentile, James M. Gentile Biology Department Hope College Holland, MichiganSearch for more papers by this author James M. Gentile, James M. Gentile Biology Department Hope College Holland, MichiganSearch for more papers by this author First published: 1988 https://doi.org/10.1002/em.2860120214AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume12, Issue21988Pages 269-270 RelatedInformation
This report puts into perspective a series of exploratory statistical analyses carried out on the major genotoxicity data bases. While large compilations of data, even though computerized, suffer from their own size and are quite intractable to scientific reflection and judgement, the multivariate data analysis methods used by us are specifically designed for reorganising the information in a rational way and highlighting the underlying regularities of the data. The analyses reported here refer to the following data bases: the International Program for the Evaluation of Short-Term Tests for Carcinogens, the International Program on Chemical Safety Collaborative Study on In Vitro Assays, the Gene-Tox data base, and a subset of the U.S. National Toxicology Program data. Although the various data bases consisted of different sets of chemicals and had different underlying rationales, a number of invariant associations among short-term test performances were highlighted. The overall evidence indicated that the traditional classification of assays (according to the criteria of genetic end-point and phylogenetic position of the assays) was in contrast with the actual, operational similarities among assay performances, in that the experimental responses of the tests to the large variety of chemicals under consideration pointed to an alternative classification scheme. This consisted of three major classes: 1) a class comprising the in vivo assays; 2) a class grouping together many of the most widely used in vitro assays (Salmonella, chromosomal aberrations, and sister chromatid exchanges in Chinese hamster ovary cells, the various mutation tests in mammalian cell systems, etc.); 3) a second in vitro assay class (with Syrian hamster embryo cell transformation, Saccharomyces cerevisiae XV185-14C, B. subtilis rec-, Escherichia coli pol A). Such classes had clearly differentiated features with respect to carcinogenicity prediction. The implications of these findings for the current debate on mutagenicity testing are discussed.
Two dyes (C.I. Solvent Yellow No. 33 and a mixture of C.I. Solvent Yellow No. 33 and C.I. Solvent Green No. 3) were tested for mutagenicity in the Salmonella reversion assay and the L5178Y/TK+/- mouse lymphoma assay, and also for sister chromatid exchange (SCE) induction in vivo in C57B1/6J mice. In addition, a greater than 99.9% pure sample of the yellow dye [2-(2'-quinolyl)-1,3-indandione] was tested with and without exogenous activation in the Salmonella reversion assay and the L5178Y/TK+/- mouse lymphoma assay. Neither C.I. Solvent Yellow No. 33 nor the C.I. Solvent Yellow No. 33 and Solvent Green No. 3 mixture was positive for inducing SCEs in vivo. All three dyes were tested in the standard plate incorporation test in seven Salmonella strains TA98, TA100, TA102, TA104, TA1535, TA1537, and TA1538. The dyes were negative with and without exogenous activation in TA98, TA1535, and TA1538. One test with TA1537 was positive with the greater than 99.9% purified yellow dye. All three dyes gave weakly positive results (less than a twofold increase) with S-9 in TA100 and were clearly positive in TA102 and TA104 both with and without S-9. They also induced mutation at the thymidine kinase locus in mouse lymphoma cells, produced both large- and small-colony trifluorothymidine-resistant mutants, and were clastogenic. The purified yellow dye was further tested for SCE induction in mouse lymphoma cells and was determined to give a slightly positive response in the presence of S-9.
The kinetics of micronucleus (MN) induction and decline in blood normochromatic erythrocytes (NCE) of mice subchronically exposed to benzene was investigated during and after exposure. Swiss (ICR) male mice (10/group) were given 0.0, 36.6, 73.2, and 146.4 mg/kg body weight benzene by gavage daily for 14 days, except for days 5 and 10. The frequency of MN increased significantly (P less than .001) during benzene treatment as a function of both concentration and time. Eleven days after exposure the levels of MN were higher than those observed at the end of exposure. After an initial rapid decline in the frequency of MN from 11 to 18 days postexposure, the decline became linear with time through 60 days postexposure. Using linear regression analysis, the MN level in each treatment group was predicted to reach control levels by approximately 85 days post-treatment. Dose-dependent suppression and recovery of erythropoiesis, estimated by polychromatic erythrocyte frequency, were observed in the 1st and 2nd weeks of exposure, respectively. Red blood cell (RBC) production was markedly increased in the first 3 weeks after benzene treatment. At later times the rate of production of the RBC returned to normal and may account for the linear decline observed in MN frequency. This research indicates that the frequency of MN is dose and duration dependent, while the decline in MN frequency after the end of benzene exposure can be related to changes in the kinetics of erythropoiesis.
The human carcinogen and nitrogen mustard chlornaphazine (CN) has been confirmed to be mutagenic to Salmonella and, unexpectedly, the more so when evaluated in the presence of liver S9 mix. It also has been established as clastogenic to Chinese hamster lung cells exposed in vitro to dose levels greater than 2.5 micrograms/ml. Chlornaphazine subdued mice at doses of 5 g/kg, but only the occasional death occurred during the 4 days following oral administration of this dose in corn oil. Consequently, a median lethal dose level was not established. Nonetheless, dose levels of 500 mg/kg or greater gave a clear positive response in both the mouse and the rat bone marrow micronucleus assay. Although depression of erythropoeisis was observed in mice, a clastogenic response still was observed in the bone marrow 24 hr after dosing. The positive response in the rat was greater than that observed in the mouse. The present data provide a further instance of an established human carcinogen being readily detected by standard in vitro and in vivo mutagenicity assays.
The ability of nitrilotriacetic acid (NTA) to induce aneuploidy was studied in the germ line of both Drosophila and the mouse. The Free Inverted X Chromosomes (FIX) genetic system, adopting a brooding scheme, was used to detect induced aneuploidy in Drosophila, and a cytogenetic method based on chromosomal counting in secondary spermatocytes was used in the mouse. In Drosophila a highly significant (P less than 0.001) increase of aneuploidies was produced by NTA (5 x 10(-2) M), which was greater than that produced by colchicine (7.5 x 10(-6) M) and 5-fluorodeoxyuridine (10(-4) M), which were used as positive controls. Brooding effects were observed with NTA, which produced a maximum induction of chromosomal gain in brood I, suggesting a possible stage-specific action during meiosis. The ability of NTA (275 mg/kg body weight) to induce meiotic aneuploidy (hyperhaploidy) also was confirmed in the mouse (P less than 0.001), where all the aneuploidies detected were attributable to treatment of the metaphase I stage.
Two tricyclic antidepressants, amitriptyline and imipramine, were evaluated for their in vitro cytogenetic effects in human lymphocyte cultures. Peripheral blood cultures from three normal healthy donors were set up for 72 hr for each of the drugs. The drugs were added at the start (72-hr exposure), 24 hr (48-hr exposure), and 48 hr (24-hr exposure) after initiation of the cultures. The concentrations evaluated at each exposure time were 50, 250, 1,000, and 10,000 ng/ml for amitriptyline and 25, 500, and 5,000 ng/ml for imipramine. The first two concentrations correspond to the plasma levels of the respective drugs after therapeutic doses. All treatments for a donor were given at the same time. Untreated cultures served as controls for the baseline frequency of the parameters assayed. The parameters assayed were chromosome aberrations, mitotic index, and sister chromatid exchanges (SCEs). Amitriptyline was found to be nongenotoxic at plasma levels by all the parameters assayed. However, frequencies of chromosome aberrations and SCEs were significantly increased at concentrations 4 and 40 times the plasma level (1,000 and 10,000 ng/ml) although the actual increases was small. The mitotic index was not affected at any concentration. Through imipramine showed a significant increase in chromosome damage at the upper plasma level and at concentrations higher than that, SCE frequency was significantly increased only at concentration higher than the plasma level (5,000 ng/ml), the actual increase being small for both these parameters. The mitotic index was not affected at any concentration. These results suggest that amitriptyline may be a slightly safer drug than imipramine from a genetic point of view.
Eleven mutagenic heterocyclic amines, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]-indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3]indole (Trp-P-2), 2-amino-6-methyl-dipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1), 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2), 2-amino-9H-pyrido[2,3-b]indole (A alpha C), 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeA alpha C), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo [4,5-f]quinoline (MeIQX), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-diMeIQX), and 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-diMeIQX), were studied for genotoxicity in the hepatocyte/DNA repair test employing hepatocytes of male rats, male and female mice, and male hamsters. In these four assay systems, all compounds elicited DNA repair in at least three systems, except Trp-P-2, which was uniformly inactive. However, there were several significant differences in the responses of different systems. Rat and hamster hepatocytes responded to nine of the ten genotoxic compounds with the exception of Glu-P-2. Male and female mouse hepatocytes responded to Glu-P-2, whereas female, but not male, mouse hepatocytes responded to MeIQX and 4,8-diMeIQX. These results illustrate species and sex differences in response to these heterocyclic amines and suggest that a number of these compounds are carcinogenic in hamsters, as they have been in rats and mice.
By comparing fibroblast strains derived from individuals exhibiting chromosome instability and/or mutagen hypersensitivity (Cockayne syndrome, ataxia telangiectasia, and Fanconi anemia) with strains derived from healthy donors, the fibroblast micronucleus assay has been established as a reproducible measure of the genotypic variation in spontaneous or mitomycin C (MMC)-induced chromosomal instability. The patient strains that were moderately or exquisitely sensitive to MMC, whereas the mildly sensitive strain (Cockayne syndrome) overlapped with the control range. The reproducibility of the assay was evaluated within and between experiments. Paired comparison analyses between duplicate cultures and between repeat experiments failed to show any significant differences between micronucleus frequencies within strains, whereas a significant differences in the spontaneous micronucleus frequencies between strains was observed. In addition to its value as a test system for genotoxins, the fibroblast micronucleus assay may be useful for investigating genetically determined hypersensitivity to mutagens, elevated spontaneous chromosomal breakage, and chromosome segregation errors.
Environmental MutagenesisVolume 12, Issue 4 p. 349-352 Commentary Computer assisted short-term test battery design: Some answers (reply to john ashby's commentary in environmental and molecular mutagenesis) Fanny K. Ennever, Corresponding Author Fanny K. Ennever Department of Environmental Health Sciences, Case Western Reserve University School of Medicine, Cleveland, OhioDepartment of Environmental Health Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106Search for more papers by this authorHerbert S. Rosenkranz, Herbert S. Rosenkranz Department of Environmental Health Sciences, Case Western Reserve University School of Medicine, Cleveland, OhioSearch for more papers by this author Fanny K. Ennever, Corresponding Author Fanny K. Ennever Department of Environmental Health Sciences, Case Western Reserve University School of Medicine, Cleveland, OhioDepartment of Environmental Health Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106Search for more papers by this authorHerbert S. Rosenkranz, Herbert S. Rosenkranz Department of Environmental Health Sciences, Case Western Reserve University School of Medicine, Cleveland, OhioSearch for more papers by this author First published: 1988 https://doi.org/10.1002/em.2860120403Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References Ashby J (1988): Computer assisted short-term test battery design: Some questions. Environ Mol Mutagen 11: 443–448. Ashby J, Tennant RW (1988): Chemical structure, Salmonella mutagenicity and extent of carcinogenicity as indicators of genotoxic carcinogenesis among 222 chemicals tested in rodents by the U.S. NCI/NTP. Mutat Res 204: 17–115. Ashby J, Klopman G, Rosenkranz HS (1988): Testing and predictivity of CASE for the mutagenicity and carcinogenicity of K and Bay region polycyclic aromatic hydrocarbons. Mutagenesis (in press). Ennever FK, Rosenkranz HS (1986a): Evaluating batteries of short-term genotoxicity tests. Mutagenesis 1: 293–298. Ennever FK, Rosenkranz HS (1986b): Short-term test results for NTP non-carcinogens: An alternate, more predictive battery. Environ Mutagen 8: 849–865. Ennever RK, Rosenkranz HS (1987): Prediction of carcinogenic potency by short-term genotoxicity tests. Mutagenesis 2: 39–44. Ennever FK, Rosenkranz HS (1988a): Influence of the proportion of carcinogens on the cost effectiveness of short-term tests. Mutat Res 197: 1–13. Ennever FK, Rosenkranz HS (1988b): Indirect estimates of the sensitivity and specificity of the Salmonella assay. Environ Mol Mutagen 11 (Suppl 11): 32 (abstract). Ennever FK, Noonan TJ, Rosenkranz HS (1987): The predictivity of animal bioassays and short-term genotoxicity tests for carcinogenicity and non-carcinogenicity to humans. Mutagenesis 2: 73–78. Frierson MR, Klopman G, Rosenkranz HS (1986): Structure-activity relationships (SARs) among mutagens and carcinogens: A review. Environ Mutagen 8: 283–327. Klopman G, Rosenkranz HS (1984): Structural requirements for the mutagenicity of environmental nitroarenes. Mutat Res 126: 227–238. Klopman G, Frierson MR, Rosenkranz HS (1985): Computer analysis of toxicological data bases: Mutagenicity of aromatic amines in Salmonella tester strains. Environ Mutagen 7: 625–644. Rosenkranz HS, Frierson MR, Klopman G (1986): Computer-automated prediction of the mutagenicity of benzidine, 4,4′-diaminoterphenyl, 4-dimethylaminoazo-benzene and 4-cyanodimethylaniline: Comparison with the results of the Second UKEMS Collaborative Study. Mutagenesis 1: 275–282. Tu A, Hallowell W, Pallotta S, Sivak A, Lubet RA, Curren RD, Avery MD, Jones C, Sedita BA, Huberman E, Tennant R, Spalding J. Kouri RE (1986): An interlaboratory comparison of transformation in Syrian hamster embryo cells with model and coded chemicals. Environ Mutagen 8: 77–98. Citing Literature Volume12, Issue41988Pages 349-352 ReferencesRelatedInformation
SRI used the L5178Y mouse lymphoma cell forward mutation assay to determine the mutagenic activity of 63 coded chemicals from 16 chemical classes. Replicate experiments were performed to assess the reproducibility of the assay within the laboratory. The evaluations (positive or negative) of the first two repeat experiments with the chemicals were the same for 116 (87%) of 134 tests. Evaluational differences between the first two experiments were fewer in the presence of induced S9 (6 tests) than in the absence of S9 (12 tests). The most commonly observed variability was the magnitude of positive mutagenic responses; this may be attributed to factors such as compound solubilities, S9 activation conditions, and differential recovery of mutant cells. Some consistency was observed in the responses of compounds of various chemical classes. Generally, antibiotics (ABO) and the azo dyes, azoxy and hydrazo compounds, diazoalkanes, nitriles and azides (AZO), were mutagenic with S9; alkyl, acyl, and aryl halides, halogenated ethers, and halohydrins (HAL) were more strongly mutagenic with than without S9; and monofunctional polycyclic aromatic hydrocarbons and fluorenones (PAH) were mutagenic only with S9. Amine-1-oxides (AMO), alkyl and aryl epoxides (EPO), and nitroalkanes, nitroaromatics, nitroquinolines, nitrofurans, and nitroimidazoles (NIT) were mutagenic with and without S9; amides, sulfonamides, aromatic amines, aliphatic amines, hydroxylamines, and benzidine and its derivatives (AMI) were mutagenic without S9; and methyl carbamate (the only monofunctional carbamate) and thioureas (CBM) induced a negative response under both conditions.
Tetracycline and chloramphenicol increase the number of mutant colonies of strain TA102, which carries the reverting gene on the plasmid pAQ1. Determination of the plasmid content by agarose gel analysis shows that the increase of the mutant colony number is paralleled closely by an increase of the number of pAQ1 plasmids per cell, indicating that the two compounds do not increase the frequency of mutants "per gene," but only enhance the number of the genes at which mutations can occur. Thus, not considering the molecular processes could result in mistakenly attributing the increase in the number of mutants per plate (respective to the number of mutants per cell) to a mutagenic activity of the antibiotics.
Seventy-two chemicals were tested for their mutagenic potential in the L5178Y tk+/- mouse lymphoma cell forward mutation assay, using procedures based upon those described by Clive and Spector (Mutat Res 44:269-278, 1975) and Clive et al. (Mutat Res 59:61-108, 1979). Cultures were exposed to the chemicals for 4 hr, then cultured for 2 days before plating in soft agar with or without trifluorothymidine (TFT), 3 micrograms/ml. The chemicals were tested at least twice. Significant responses were obtained with allyl isothiocyanate, p-benzoquinone dioxime, benzyl acetate, 2-biphenylamine HCl, bis(2-chloro-1-methylethyl)ether, cadmium chloride, chlordane, chlorobenzene, chlorobenzilate, 2-chloroethanol, chlorothalonil, cytarabine.HCl, p,p'-DDE, diazinon, 2,6-dichloro-p-phenylenediamine, N,N-diethylthiourea, diglycidylresorcinol ether, 2,4-dimethoxy aniline.HCl, disperse yellow 3, endosulfan, 1,2-epoxyhexadecane, ethyl acrylate, ethyl benzene, ethylene thiourea, F D and C yellow Number 6, furan, heptachlor, isophorone, mercuric chloride, 4,4'-methylenedianiline.2 HCl, methyl viologen, nickel sulfate.6H2O, 4,4'-oxydianiline, pentachloroethane, piperonyl butoxide, propyl gallate, quinoline, rotenone, 2,4,5,6-tetrachloro-4-nitro-anisole, 1,1,1,2-tetrachloroethane, trichlorfon, 2,4,6-trichlorophenol, 2,4,5-trimethoxybenzaldehyde, 1,1,3-trimethyl-2-thiourea, 1-vinyl-3-cyclopetene dioxide, vinyl toluene, and ziram. Apart from 2-biphenylamine.HCl, 2-chloroethanol, disperse yellow 3, ethylene thiourea, FD and C yellow number 6, phenol, and 1,1,2-tetrachloroethane, rat liver S9 mix was not a requirement for these compounds. Chemicals not identified as mutagens were acid red, 11-aminoudecanoic acid, boric acid, 5-chloro-o-toluidine, coumaphos, cyclohexanone, decabromodiphenyl oxide, di(2-ethylhexyl)adipate, ferric chloride, fluometuron, melamine, monuron, phenesterin, phthalimide, reserpine, sodium dodecyl sulfate, 4,4-sulfonyldianiline, tetrachloroethylene, and zearalenone. The assay was incapable of providing a clear indication of whether some chemicals were mutagens; these were benzyl alcohol, 1,4-dichlorobenzene, phenol, succinic acid-2,2-dimethyl hydrazide, and toluene.
The L5178Y mouse lymphoma cell mutagenesis assay is used to detect the mutagenic activity of chemicals in a mammalian cell system. To evaluate this assay we compared the results of assays performed independently on 63 chemicals by laboratories at SRI International and Litton Bionetics, Inc. The two laboratories used similar protocols. The solvent and positive control mutant frequencies and cloning efficiencies obtained by the two laboratories were similar, which justified the use of the same quality-control criteria and analytical procedures for analyzing the results from both laboratories. The rate of concordance between the two laboratories was 92% for tests in the absence of S9 activation and 95% for tests in its presence. The results of the assays agreed for 57 of the 63 chemicals; three chemicals could not be compared because there were questionable calls in at least one of the laboratories; the results disagreed for the three remaining chemicals. The concordance rate for these overall assay evaluations was 95%. The interlaboratory concordance rates were similar to concordance rates for replicate experiments within the laboratories (96% at LBI, 94% at SRI). The mouse lymphoma cell mutagenicity results are concordant with the rodent chronic assay results in 78% of 50 chemicals and with the Salmonella assay results in 79% of 56 chemicals. Fifteen carcinogens were examined for genotoxic effects in mouse lymphoma, Salmonella, Chinese hamster ovary (CHO) chromosomal aberration, and CHO sister chromatid exchange assay. Eight of these were positive in all four assays. Of the seven noncarcinogens that were tested in these four assays, none was negative in all four. The main conclusion to be drawn from this study is that the mouse lymphoma cell forward mutation assay, as performed and evaluated in this study, detects chemical mutagenicity in a manner that is highly consistent with other genetic endpoints as well as rodent carcinogenicity studies. Thus the assay quality control and response criteria established in this study led not only to a high degree of reproducibility but also to an apparently reliable detection of mutagenic activity.
