Low Tumorigenic Response to 3,2′‐Dimethyl‐4‐aminobiphenyl Administration in the Prostate of Rats Castrated at Birth

Six‐week‐old rats which had been orchiectomized at birth were given 3,2′‐dimethyl‐4‐aminobiphenyl (DMAB) at various doses combined with a stimulus to prostate epithelial cell proliferation in the form of oral administration of methyltestosterone (MT) for 4 weeks. Thereafter MT treatment was continued or the animals received subcutaneous implants of testosterone propionate (TP) and were maintained until sacrifice at week 60. Although prostatitis and prostatic enlargement were frequently observed, especially in the TP group, numbers of atypical hyperplastic lesions were low and only one prostatic carcinoma in situ developed. Thus, despite the presence of proliferation, castration brought about a significant reduction in susceptibility to DMAB.