The superiority of hamster liver microsomal fraction for activating nitrosamines to mutagens in Salmonella typhimurium.

A number of nitrosamines which were carcinogenic in rats were not activated to mutagens in the Salmonella/mammalian microsome assay by the addition of the rat liver microsomal fraction. Some of these nitrosamines induced tumors in the liver of rats and others were carcinogenic to different organs of the rat. Most of these nitrosamines were activated to mutagens by hamster liver microsomal fraction. The use of the hamster preparation showed some compounds to be of very high mutagenic potency. In a few cases the nitrosamines mutagenic with hamster liver activation were more potent carcinogens in the hamster than in the rat. The compounds which were non-mutagenic to Salmonella with either rat or hamster liver activation included the liver carcinogens nitrosomethylethylamine, nitrosodiethanolamine and nitrosoethanolisopropanolamine, the esophageal carcinogens nitrosomethylneopentylamine, nitrosomethylaniline, nitrosomethyl-4-fluoroaniline, nitrosothiomorpholine and nitrosophenylbenzylamine, and the bladder carcinogens nitrosomethyl-3-carboxypropylamine and nitrosodiphenylamine.