SLIGHT PROMOTION EFFECTS OF INTERMITTENT ADMINISTRATION OF TESTOSTERONE PROPIONATE AND OR DIETHYLSTILBESTROL ON 3,2'-DIMETHYL-4-AMINOBIPHENYL-INITIATED RAT PROSTATE CARCINOGENESIS/

In order to determine the effects of intermittent hormonal manipulatio n on the promotion stage of rat prostate carcinogenesis, testosterone and/or estrogen were administered to F344 rats for 40 weeks after 20-w eeks treatment with the prostate a carcinogen, 3,2'-dimethyl-4-aminobi phenyl. For this purpose testosterone propionate (TP) and diethylstilb estrol (DES) were introduced into silastic tubes, 2- and 0.5-cm long, respectively, and implanted into the subcutis for seven repeated cycle s of 30 days treatment and 10 days withdrawal. Intermittent administra tion of TP resulted in suppression of veneral prostate adenocarcinoma development and slight but non-significant increases in the incidences of invasive carcinomas of the lateral prostate and seminal vesicles. Intermittent administration of DES completely suppressed tumorigenesis in all sites and the combination of TP and DES generally inhibited pr ostate tumor development. Thus, under the present experimental conditi ons, no strong enhancing effects of cyclic hormonal manipulation were observed on rat prostate carcinogenesis. Indeed, the opposite appeared to be the case. (C) 1998 Elsevier Science Ireland Ltd.