Carcinogenicity of 3-methyl-2-naphthylamine and 3,2'-dimethyl-4-aminobiphenyl to the bladder and gastrointestinal tract of the Syrian golden hamster with atypical proliferative enteritis.

3,2'-Dimethyl-4-aminobiphenyl (DMAB) and 3-methyl-2-naphthylamine (MeNA) were each administered to groups of 25 male noninbred Syrian golden hamster weanlings in doses of 100 mg/kg body weight by weekly sc injections for a total of 38 injections over 18--22 months. DMAB produced a high incidence of urinary bladder epithelial neoplasms and intestinal neoplasms. Other neoplasms included squamous papilloma of nonglandular stomach, lymphoma-leukemias, and squamous cell carcinomas of the ear duct and skin. With MeNA, urinary bladder epithelial neoplasms occurred but no intestinal tumors. Also present were soft-tissue sarcomas at the injection site, papilloma of forestomach, and lymphoma-leukemias. Most hamsters in both groups as well as the control group had a chronic form of atypical proliferative enteritis that affected the small or large intestine. The occurrence of intestinal tumors with DMAB could be related to sensitizing effect of increased intestinal mucosal proliferation. Apart from this effect, hamsters displayed a distinct susceptibility to bladder carcinogenesis by these aromatic amines.