Lobe specific effects of testosterone and estrogen on 3,2 '-dimethyl-4-aminobiphenyl-induced rat prostate carcinogenesis

We have previously shown that chronic administration of a pharmacological d ose of testosterone propionate (TP) after treatment with the carcinogen, 3, 2'-dimethyl-4-aminobiphenyl (DMAB), results in development of invasive and metastatic adenocarcinomas arising from the dorso-lateral and anterior pros tate, as well as the seminal vesicles. Co-administration of ethinyl estradi ol (EE) with TP increased the yield of carcinomas in the lateral and anteri or lobes. In the present experiment, male F344 rats were treated with DMAB for 20 weeks and then co-administered a pharmacological dose of TP together with various doses of EE for 40 weeks. Without hormone(s) administration, carcinomas were confined to the ventral prostate and all were of intra-acin ar type. TP administration suppressed development of the ventral prostate c arcinomas but caused invasive carcinomas of the lateral and anterior lobes and of seminal vesicles and intra-acinar carcinomas in the dorsal prostate. The appearance of carcinomas in the lateral and anterior prostate was incr eased by co-administration of EE in a dose-related fashion but carcinomas o f the seminal vesicles were inversely reduced. The suppressive influence of TP on ventral carcinoma development was overcome by only the highest dose of EE. It is concluded that estrogen can modify the enhancing effects of TP on induction of rat prostate and seminal vesicle carcinomas in a dose-rela ted fashion with lobe specificity. (C) 2000 Elsevier Science Ireland Ltd. A ll rights reserved.