Carcinogenicity of 3'-hydroxymethyl-N,N-dimethyl-4-aminoazobenzene in rat liver.

Male Sprague-Dawley rats were fed a cube diet containing 2.51 mmol/kg 3'-hydroxymethyl-N,N-dimethyl-4-aminoazobenzene (3'-CH2OH-DAB) for a period of 1 or 3 months. (This is the molar equivalent of 0.06% 3'-Me-DAB in the diet). The oral administration of 3'-CH2OH-DAB for 3 months resulted in a high incidence of liver tumors at 6 months and the 1 month feeding also caused the development of liver tumors. Histologically, the tumors were cholangiocellular carcinomas and hepatocellular carcinomas. The development of tumors in other sites was not seen. Consequently, 3'-CH2OH-DAB, a recently identified metabolite of 3'-Me-DAB, is a potent hepatocarcinogen.