The effect of 4-substitution on the carcinogenicity of nitrosopiperidine.

Nitrosopiperidine and three derivatives substitute in the 4-position were fed to female F 344 rats in drinking water at equimolar concentration. The substituents were phenyl, cyclohexyl and tertiary-butyl. Like nitroso-piperidine, the t-butyl-and phenyl-derivatives induced tumors of the upper gastrointestinal tract (esophagus, forestomach and tongue), but the animals given nitroso-piperidine died earlier and after a smaller total dose. The rats given 4-phenylnitrosopiperidine also had a high incidence of tumors of the liver, both hepatocellular carcinomas and angiosarcomas. These tumors were absent from untreated animals of this strain. In contrast, no induced tumors were observed in rats treated with 4-cyclohexylnitrosopiperidine.