Immunocytochemical analysis of androgen receptor along the ducts of the separate rat prostate lobes after androgen withdrawal and replacement.

Abstract

Autoregulation of androgen receptors (AR) in the rat prostate gland has previously been shown to be lobe specific. Saturation ligand-binding assays revealed that AR fell to very low levels in the ventral and dorsal prostate within 7 days after castration, whereas lateral lobe AR were present at intact levels at that time. To study this differential response further, we herein analyzed AR in the separate prostate lobes by indirect immunocytochemistry after castration and testosterone replacement to adult rats. The ventral and dorsal lobes each contain one type of duct, whereas the lateral lobe is composed of two ductal systems, which were separated as LP1 and LP2. Frozen ducts were sectioned longitudinally to reveal the proximal-distal orientation. Sections were stained for AR with PG-21 antibody against rat AR. Within 2 days after castration, ventral and dorsal lobe immunoreactive nuclear AR was markedly decreased in staining intensity in the secretory epithelium compared to that in the intact rat and was absent in all stromal cells. Epithelial immunostaining continued to decline to a weak punctate nuclear signal by day 7, which further dissipated by day 21. Proximal and intermediate regions of the ducts were largely devoid of AR signal after castration, whereas residual nuclear staining was most apparent in epithelial cells of the distal ductal region. By day 7 and beyond, specific cytoplasmic staining for AR was also observed in distal tip epithelial cells. In the lateral lobe, LP1 ducts rapidly lost all AR immunostaining upon androgen withdrawal. In marked contrast, epithelial cells in the LP2 ducts retained AR immunostaining at all time points after androgen withdrawal at a signal intensity equivalent to that in the intact animal. Within 15 min after testosterone injection to 14-day castrate rats, considerable nuclear AR immunostaining was apparent within the distal tip epithelial cells of the ventral, dorsal, and lateral LP1 lobes. Cytoplasmic signal was noticeably reduced at this time. With increasing time after continued testosterone replacement, nuclear AR signal intensity increased, so that by 72 h, nuclear AR signal in all secretory epithelial cells approached the staining intensity observed in intact rats. AR immunostaining returned to smooth muscle and fibroblastic stromal cells within 1-3 days after testosterone replacement. In summary, immunodetectable AR declined in the ventral, dorsal, and LP1 prostate ducts after castration-induced androgen withdrawal and returned upon testosterone replacement, which further indicates that androgen up-regulates AR protein within these prostatic regions.(ABSTRACT TRUNCATED AT 400 WORDS)