Mutagenicity of cyclic nitrosamines in Escherichia coli following activation with rat liver microsomes

Ten cyclic nitrosamines were tested for mutagenicity in Escherichia coli after incubation in vitro with 9000 X g microsomal supernatants prepared from rat liver, and the results were compared with carcinogenicity data from the same species. None of the compounds was mutagenic in the absence of microsomes. Seven carcinogenic compounds, nitrosopyrrolidine, nitrosopiperidine, nitrosohexamethyleneimine, nitrosoheptamethyleneimine, nitrosomorpholine, dinitrosopiperazine, and dinitrosohomopiperzine, were mutagenic after microsomal activation. One compound, nitrosohepamethyleneimine, was toxic to the bacteria. Two noncarcinogens, 1-nitrosopiperazine and 1-methyl-4-nitrosopiperazine, and 1 strong carcinogen, 2,6-dimethyldinitrosopiperazine, were not mutagenic with or without microsomal incubation. The liver microsome preparation activated equally well those compounds that are liver carcinogens in Sprague-Dawley rats, and compounds for which the liver is not a target organ.