DIRECT EFFECTS OF TESTOSTERONE, DIHYDROTESTOSTERONE AND ESTROGEN ON 3,2'-DIMETHYL-4-AMINOBIPHENYL-INDUCED PROSTATE CARCINOGENESIS IN CASTRATED F344 RATS

The present experiment was carried out to explore the effect of endoge nous androgen on rat prostate carcinogenesis induced by 3,2'-dimethyl- 4-aminobiphenyl (DMAB) and testosterone propionate (TP) or 5 alpha-dih ydrotestosterone (DHT) with or without ethinyl estradiol (EE). In orde r to eliminate the influence of endogenous androgen, F344 rats were or chiectomized just after initiation with the prostate carcinogen, DMAB, and then given TP, DHT, TP plus EE or DHT plus EE for 40 weeks. The r esults demonstrated that while administration of TP following DMAB tre atment causes invasive carcinomas in the lateral and anterior prostate and seminal vesicles, DHT does not exhibit equivalent effects. Synerg istic enhancement was also evident with TP plus EE, but not with DHT p lus EE. The incidences of prostatic and seminal vesicle lesions in all groups of the present experiment, except for the group given castrati on without hormonal supplement, were equivalent to those previously fo und in non castrated animals. Therefore, the present findings indicate that endogenous testosterone may not be required for promotion by TP/ EE of DMAB-initiated prostate carcinogenesis and that it may not contr ibute to the actions of DHT.