Carcinogenesis in F-344 rats by nitrosobis(2-oxopropyl)amine and related compounds administered in drinking water

Three asymmetric nitrosamines related to nitrosobis-(2-oxopropyl)-amine (BOP) were given to female F344 rats in drinking water to assess the significance of other alkyl groups on the carcinogenic expression by the 2-oxopropyl group. Nitroso-oxopropylethanolamine (OPE) was weakly carcinogenic, leading to little life-shortening and to induction of tumors (most of them liver neoplasms) in less than half of the treated animals. BOP under these conditions induced a high incidence of hepatocellular carcinomas and hemangiosarcomas of the liver together with lung adenomas in most animals. At the same dose rate nitrosohydroxypropyl-oxopropylamine (HPOP) induced hepatocellular carcinomas, lung carcinomas, and carcinomas of the esophagus with a high incidence; life-shortening was greater with HPOP than with BOP. At a higher dose rate HPOP again induced a high incidence of esophageal carcinomas, and of liver neoplasms, but more animals had hemangiosarcomas than hepatocellular carcinomas. Nitrosodihydroxypropyl-oxopropylamine (DHPOP) increased the mortality rate due to tumors by much more than the other three compounds, but induced mainly tumors of the upper gastrointestinal tract and no neoplasms in the liver. These results do not support the concept that BOP acts through reduction to HPOP, but suggest rather that the nature of the substituents other than 2-oxopropyl in the analogs of BOP has a profound influence on the potency and organ-specificity of the carcinogen. It is probable that pharmacokinetics and the specificity of activation of the particular molecular structures play an important role.