Carcinogenicity and mutagenicity testing of three isomeric N-nitroso-N-methylaminopyridines in rats.

Three isomeric N-nitroso-N-methylaminopyridines (NMPY's) were investigated for their carcinogenic activity in BD VI rats following chronic oral administration and for their mutagenic properties in the Ames assay. On the basis of postulated reaction mechanisms, it was expected that 3-NMPY would react differently than 2- and 4-NMPY, but the outcome of both carcinogenicity and mutagenicity assays did not show this. 2-NMPY induced tumors of the esophagus and possibly also of the liver; 3- and 4-NMPY had no activity as carcinogens under the experimental conditions used. Similarly, high concentrations of 2-NMPY showed mutagenic activity toward Salmonella typhimurium TA100, whereas 3- and 4-NMPY did not have such an effect.