Androgen ablation results in differential regulation of transforming growth factor-beta isoforms in rat male accessory sex organs and epididymis

Abstract

The male accessory sex organs and epididymis regress following androgen depletion, although the onset of apoptosis varies temporally depending upon the tissue type. Transforming growth factor-beta1 (TGF-beta1) is an androgen-repressed gene and believed to be an apoptotic agent in the regressing rat ventral prostate (VP). Hence, in order to investigate the status of TGF-beta isoforms following castration in androgen-dependent tissues other than VP, this study was undertaken. Northern blot analysis using total RNA from these tissues of intact animals showed higher levels of TGF-beta1 expression as compared with VP, indicating a function other than that of an apoptotic agent for this isoform. Following orchiectomy, TGF-beta1 was induced in all organs studied and the levels were highest at day 3 following castration in seminal vesicle (SV) and the epididymis and decreased by day 5 despite the absence of androgens. This observation implies that TGF-beta1 might not be a truly androgen-repressed gene in these tissues. TGF-beta2 was up-regulated in VP, SV, caput and corpus epididymis but was undetectable in the dorsolateral prostate and cauda epididymis. On the other hand, TGF-beta3 expression was refractory to the androgen status in corpus epididymis and SV but was up-regulated in the remaining tissues. The castration-induced induction of mRNAs was attenuated after exogenous androgen administration. Most importantly, all the isoforms differed significantly in the time and magnitude of induction following castration, suggesting that a single hormone, testosterone, modulates the expression of TGF-betas in an isoform- and tissue-specific manner.