Effects of Age on Multiple Organ Carcinogenesis Induced by 3,2′‐Dimethyl‐4‐aminobiphenyl in Rats, with Particular Reference to the Prostate

The effects of age on multi‐organ carcinogenesis induced by 3,2′‐dimethyl‐4‐aminobiphenyl (DMAB) in male F344 rats were examined. Groups of 5‐, 35‐, and 65‐week‐old animals were given 4 weekly sc injections of DMAB at a dose of 200 or 150 mgAg body weight. Prostate carcinomas were induced in 8 to 19% of rats treated, no significant differences in the incidence between different ages being observed. Tumors in the small intestine, skin, pancreas and peritoneum, however, developed more frequently in young than in old animals, whereas higher incidences of testis, preputial and mammary gland lesions were found in the 35‐ and/or 65‐week‐old groups. Colon and Zymbal gland carcinogenesis did not reveal any age dependence.