Relationship between carcinogenicity and in vitro metabolism of nitrosomethylethylamine, nitrosomethyl-N-butylamine, and nitrosomethyl-(2-phenylethyl)amine labeled with deuterium in the methyl and alpha-methylene positions.

With the use of rat liver preparations, the in vitro microsomal metabolism of methylethylnitrosamine, methyl-n-butylnitrosamine, and methyl(2-phenylethyl)nitrosamine labeled with deuterium in the methyl and alpha-methylene positions has been compared with that of the parent (unlabeled) compounds. All three forms of the liver carcinogen methylethylnitrosamine are metabolized with two sets of kinetic constants. Examination of these kinetic constants suggests that both methylation and ethylation of cellular nucleophiles might be important in the carcinogenic action of these nitrosamines. The esophageal carcinogen, methyl(2-phenylethyl)nitrosamine, gave only one set of kinetic constants during metabolism. The metabolism of the three methylbutylnitrosamines gave results similar to that of the three methylethyl nitrosamines. Except for metabolism of d2-methylbutylnitrosamine to butyraldehyde, two sets of kinetic constants were found. Approximately equivalent amounts of methylating species were produced from d3-methylbutylnitrosamine and d0-methylbutylnitrosamine.