The carcinogenicity of p-monomethylaminoazobenzene in various diets and the activity of this dye relative to p-dimethylaminoazobenzene.

In studies on the carcinogenic activity of compounds related to podimethylaminoazobenzene it has been observed that p-monomethylaminoazobenzene is about as active as the dimethyl compound (10, 17). More recently Giese, Miller, and Baumann (4) showed that when these compounds were fed ad libitum at either of two levels for 2 89 to 3 89 months, the monomethyl compound always caused a higher incidence of hepatomas than the dimethyl compound. However, rats fed p-monomethylaminoazobenzene voluntarily consumed more diet and, therefore, more of the carcinogen. Other studies (13) demonstrated that p-dimethylaminoazobenzene was reversibly demethylated in vivo to p-monomethylaminoazobenzene, and that the latter compound appeared to be irreversibly demethylated to p-aminoazobenzene. Since both methylated compounds are present in the animal body when either dye is fed, it is difficult to determine which is the closer to the true carcinogen. The present studies were designed with this question in mind. The effect of various diets on the carcinogenicity of p-monomethylaminoazobenzene was determined, and a more rigid comparison was made of the activity of the monomethyl and dimethyl dyes. The diets selected were of two types. In the first group were diets high in riboflavin or in which hydrogenated coconut oil was substituted for corn oil; these rations are known to inhibit the induction of tumors