Carcinogenicity and mutagenicity of 4-nitropyridine 1-oxide derivatives.

Carcinogenicity and mutagenicity of 4-nitropyridine 1-oxide (4-NPO) and 7 kinds of its alkyl derivatives were tested on mice and on Salmonella typhimurium strains and Escherichia coli strains. 3-Methyl-4-NPO is the most potent carcinogen, followed by 3-ethyl-4-NPO and then 4-NPO. Mutagenicity was most potent in 3-methyl, 2,3-dimethyl, and 2,5-dimethyl derivatives, moderate in 4-NPO and 2-methyl and 2,6-dimethyl derivatives, and to a least extent in 3,5-dimethyl-4-NPO. Structure-mutagenicity relationship was discussed on the basis of molecular mechanism of the carcinogenesis of 4-nitroquinoline 1-oxide. Quantitative relationship between mutagenicity and carcinogenicity was not strictly found among the compounds examined.