MICROSOME-MEDIATED MUTAGENESIS IN V79 CHINESE-HAMSTER CELLS BY VARIOUS NITROSAMINES

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 37  (4) , 1044-1050
Abstract
A [liver] microsome-mediated mutagenesis system was established with the V79 Chinese hamster [lung] cell line. The cells, grown in monolayer, were treated with various nitrosamines in the presence of a postmitochondrial fraction (S15) from rat liver and an NADH generating system for 1 h, washed and incubated for 2-3 h in fresh culture medium and then plated for toxicity and mutagenicity assays. Mutation was determined by resistance to 20 .mu.g 8-azaguanine/ml. In this assay system, the S15 fraction and cofactors by themselves were not toxic to the cells. Dose-related mutagenicity and cytotoxicity were induced by N-nitrosodimethylamine (DMN) only in the presence of the S15 fraction and cofactors. Pretreatment of rats with phenobarbitone led to an .apprx. 2-fold increase in the mutation rate over that with tissues from untreated rats with concentrations of DMN from 10-50 mM, while aminoacetonitrile pretreatment reduced the mutagenic effect. Methylcholanthrene pretreatment resulted in an increase in the mutation frequency with a higher concentration of DMN (50 mM). Various other nitrosamines were also assayed in the presence or absence of the S15 fraction from phenobarbitone pretreated rats and an NADPH generating system. With the exception of N-nitrosomethylphenylamine, the carcinogenic nitrosamines (DMN, N-nitrosodiethylamine, N-nitrosodi-n-propylamine, N-nitrosodi-n-butylamine, N-nitrosodi-n-pentylamine, N-nitrosomethyl-n-propylamine, N-nitrosomorpholine, N-nitrosopyrrolidine, N-nitroso-N''-methylpiperazine and N-nitrosomethylphenylamine) were mutagenic to the V79 Chinese hamster cells in the presence of the S15 fraction and cofactors. Neither N-nitrosodiphenylamine nor N-nitrosomethyl-tert-butylamine had a mutagenic effect. These findings show that chemical carcinogens can be tested for mutagenicity in cultured mammalian cells in the presence of a metabolic activation system. The results are disucssed in relation to the carcinogenicity and mutagenicity of these compounds in other test systems.