Carcinogenesis tests of nitroso-N-methylpiperazine, 2,3,5,6-tetramethyldinitrosopiperazine, nitrosoisonipecotic acid and nitrosomethoxymethylamine in rats.

Four nitrosamines; nitroso-N-methylpiperazine, 2,3,5,6-tetramethyldinitrosopiperazine, nitrosoisonipecotic acid and nitrosomethoxymethylamine, closely related in structure to potent carcinogens, were fed chronically to rats in drinking water for one year. No toxic effects leading to life shortening were observed. There was no significant incidence of any malignant tumor other than the endocrine tumors normally found in untreated animals of our colony. This indicated that the small changes in structure represented by these compounds were sufficient to reduce greatly, or eliminate, the carcinogenic action.