Induction of Prostate Carcinoma in Situ at High Incidence in F344 Rats by a Combination of 3,2'-dimethyl-4-aminobiphenyl and Ethinyl Estradiol

Male F344 rats were given a diet containing 0.75 ppm of ethinyl estradiol for 3 weeks and a basal diet for 2 weeks alternately 10 times, and 2 days after each change to basal diet (on the third day of feeding of the basal diet), a single s.c. injection of 50 mg/kg body weight of 3,2'-dimethyl-4-aminobiphenyl. Then they were given the basal diet until week 60 and sacrificed for histological examination. Prostatic carcinomas were found in 18 of 21 rats (85.7%) after this treatment but in only 1 of 19 rats (5.2%) maintained on normal diet throughout the experiment but given 3,2'-dimethyl-4-aminobiphenyl at the same times as the diet given to test rats. All the carcinomas were microscopic and developed in the ventral lobe of the prostate. This method may ultimately lead to a useful animal model of prostatic carcinoma.