Macromolecular binding and metabolism of the carcinogen 4-chloro-2-methylaniline

Biochemical investigations relating to the mechanism of action and mechanism of activation have been made for the carcinogen, 4-chloro-2-methylaniline. Radioactivity from 4-chloro-2-[methyl-14C]methylaniline became extensively bound to protein, DNA, and RNA of rat liver, but macromolecules of some of the other tissues examined contained little radioactivity. Enzymatic activity dependent upon reduced nicotinamide adenine dinucleotide and leading to irreversible binding to radioactivity from labeled 4-chloro-2-methylaniline to macromolecules in the reaction system was present in microsomes from rat liver. The activity was inducible by phenobarbital. Two soluble products of microsomal enzymes were identified by mass spectral analysis and chemical synthesis as 5-chloro-2-hydroxylaminotoluene and 4,4'-dichloro-2,2'-dimethylazobenzene. The hydroxylamino compound appears to be a more activated form of 4-chloro-2-methylaniline.