Induction of progesterone receptor immunoexpression in stromal tissue throughout the male reproductive tract after neonatal oestrogen treatment of rats

Oestrogen exposure of the male during fetal/neonatal life can fundamentally alter the structure and function of the reproductive system, though how is unknown. This study examined whether such treatment was able to induce a ' female' characteristic, namely immunoexpression of progesterone receptor (P R), in the reproductive system of the male. Rats were treated on postnatal days 2, 4, 6, 8, 10 and 12 with either 10, 1 or 0.1 mu g diethystilbestrol (DES) or with the vehicle (20 mu l corn oil). Groups of control and treated rats were killed on days 18, 25, 35 and 90 (= adults) and tissues fixed in Bouins for immunolocalisation studies using antisera to PR (recognises A a nd B forms) and oestrogen receptor-beta (ERP). PR immunoexpression was abse nt from all tissues studied in control rats at all ages with the exception of the parasympathetic ganglia of the prostate. In rats treated with 10 mu g DES, intense immunoexpression of PR was detected in the nuclei of stromal , but not epithelial, cells of the caput and cauda epididymis, the vas defe rens, seminal vesicles and at the base of the dorsolateral prostatic comple x (DLPC) at day 18, but was absent from the ventral prostate and from the t estis. DES induction of PR immunoexpression was evident after a single inje ction (on day 3) and at 18-35 days the intensity of immunoexpression was DE S dose-dependent; rats treated neonatally with 0.1 mu g DES showed no detec table PR immunoexpression at any age. These findings were confirmed by West ern analysis which indicated that most of the PR induced was probably the B form. Co-localisation studies, using confocal microscopy, demonstrated tha t PR and ERP frequently co-localised to the same stromal cells in the DLPC, epididymis and seminal vesicles of DES-treated rats at day 18, whereas epi thelial cells, which also expressed ERP, did not express PR. In the tissues studied, only occasional stromal cells expressed ER alpha in comparison to the more widespread expression of ER beta, although epithelial cell expres sion of ER alpha was also detected in the epididymis on day 18 (but not on day 10). In DES-treated rats, immunoexpression of PR in the reproductive tr act decreased progressively in intensity from days 18-35 and was non-detect able in adulthood. In conclusion, these findings are interpreted as evidenc e that neonatal oestrogen treatment exerts pervasive 'reprogramming' effect s throughout the reproductive system of the developing male as indicated by the induction of PR immunoexpression. This induction was restricted to str omal tissue even though both stromal and epithelial cells at most sites exp ressed ER beta and/or ER alpha. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.