title: Differential mutagenicity of N-methyl-N-nitrosocarbamate insectides in Escherichia coli strains having different DNA repair capacities.
abstract: Four isogenic strains of Escherichia coli with the same auxotrophic marker (arg Fam--namely wild-type, uvrA-, polA- and recA-) were used for testing the lethalities and mutagenicities of 1-naphthyl N-methyl-N-nitrosocarbamate (nitroso-NAC), 3-methylphenyl N-methyl-N-nitrosocarbamate (nitroso-MTMC), and 3,4-dimethylphenyl N-methyl-N-nitrosocarbamate (nitroso-MPMC). The strains recA- and polA- showed a similarly higher sensitivity to killing than wild-type and uvrA- after treatments with each of the three chemicals, whereas the strains wild-type, uvrA-, and polA- were equally mutable by these compounds at equal doses. The strain recA- was hardly mutable by nitroso-NAC, but significant levels of Arg+ mutations were observed after treatments with nitroso-MTMC and nitroso-MPMC. These and previous results suggest that both nitroso-MTMC and nitroso-MPMC are similar in their mutagenicity pattern to N-methyl-N'-nitro-N-nitrosoguanidine whereas nitroso-NAC is similar to methyl methanesulfonate or X-rays, and that the major damage to DNA of the three agents is not excisable by the uvrA+-dependent excision repair, probably methylation in DNA.
mesh_terms: D001120:Arginine / Q000235:genetics; D002219:Carbamates; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D009153:Mutagens; D010641:Phenotype
chemical_list: D002219:Carbamates; D007306:Insecticides; D009153:Mutagens; D001120:Arginine