The effect of substituents on the carcinogenicity of n-nitrosopyrrolidine in Sprague-Dawley rats.

N-Nitrosopyrrolidine and two of its derivatives were prepared and fed in drinking water to Sprague-Dawley rats to compare the effects of substituents on the carcinogenicity of the N-nitrosopyrrolidine molecule. 3,4-Dichloro-N-nitrosopyrrolidine induced esophageal tumors in 13 of 14 animals, olfactory carcinomas in 4, and a hepatocellular tumor in 1. All animals that received this compound were dead at 55 weeks after the start of the experiments. N-Nitrosopyrrolidine induced hepatocellular tumors in 26 of 29 animals and induced 1 olfactory carcinoma. Not all animals in this group were dead until 104 weeks of the experiment. 2,5-Dimethyl-N-nitrosopyrrolidine induced only 2 hepatocellular tumors in 29 animals. The alpha-methyl substitution diminished the liver carcinogenicity, while the beta chlorine substitution affected a different target organ, the esophagus, and greatly reduced the time to death with tumors.