Regional variations in the testicular dependence of prolactin binding and its possible relationship to castration‐induced involution in rat prostate gland

Abstract

Prolactin binding sites of ventral, lateral, and dorsal lobes of rat prostate were examined immunohistochemically 1, 2, 4, and 8 days after castration or sham operation. In sham-operated rats each lobe exhibited a distinct pattern of intracellular and intraluminal prolactin binding. A loss in prolactin binding from epithelial cells of ventral prostate, which was visualized postcastration, was quantitated with the aid of an image analyzer and then statistically evaluated. The proportion of ventral prostate epithelial cells devoid of prolactin binding increased from approximately 13% in sham-operated rats to approximately 29% 1 day after castration, and reached a peak level of about 71% 4 days postcastration. No loss of prolactin binding was evident in either lateral or dorsal prostate up to 8 days postcastration. Direct measurement of epithelial cell heights and subsequent statistical evaluation revealed similar regional differences in the rates and extent of prostate involution. Eight days after castration ventral prostate epithelial cell heights decreased by 56% whereas lateral and dorsal lobe epithelial cells heights decreased about 25% and 14%, respectively. The apparent relationship between testicular dependence of prostatic prolactin binding and castration-induced prostatic involution are discussed in terms of possible regional variations in the prolactin-androgen interplay in prostate.

Indomethacin decreases both prolactin binding and membrane fluidity of ventral and dorso‐lateral lobes of rat prostate gland

“…The predominance of prolactin binding in the 15 K g fraction of prostate confirms our previous observations [27] and those of Keenan et a1 [28]. It is also consistent with the possibility of intracellular prolactin binding sites in prostate which we and others have observed with immunohistochemistry [1,5,30]. It is interesting to note that the 15 K g fraction is also more fluid than the 100 K g fraction of rat prostate.…”

“…The absence of prolactin receptors in the dorso-lateral complex is difficult to reconcile with the observation that this zone, particularly the lateral lobe, is highly responsive to prolactin (reviewed in 1). Furthermore, prolactin binding in dorsal and lateral prostate have been demonstrated by immunohistochemistry [ 1,5]. The fact that dorso-lateral prolactin receptors are demonstrable in our hands could be related to the procedure we used to fractionate the tissue.…”

“…The influence of prolactin on the prostate gland has been recognized for some time [ 13. The existence of specific prolactin receptors in prostate is well documented [2,3] and is consistent with its physiological effects [4,5]. Prolactin, like other hormones, is known to modify the level of its own receptors in a variety of tissues [6-91. This has been reported to occur in a biphasic fashion with receptor upregulation being observed after administration of physiological doses of prolactin and receptor down-regulation occurring in hypoprolactinemic or hyperprolactinemic states [ 10-121. Recent studies on murine hepatic membranes suggest that prostaglandins are involved in the modulation or prolactin receptors which are paralleled by changes in membrane fluidity .…”

Proteolytic Fragmentation of Rat Prolactin by the Rat Ventral Prostate Gland

“…The dorsolateral prostate also showed low levels of PRL-degrading activity without fragment formation, suggesting that the ventral and dorsolateral lobes process PRL differently. This would be consistent with reports of regional differences in hormonal dependency and function among the lobes of the rat prostate [19]. Alternatively, the failure to detect fragments in dorsolateral prostate might merely be a reflection of the fact that proteolysis is occurring at a much lower rate.…”

Androgen Regulation of Prostate Morphoregulatory Gene Expression:Fgf10-Dependent and -Independent Pathways

“…It has been previously demonstrated that the separate lobes of the rat prostate gland exhibit differential sensitivity to androgens in terms of growth, with the ventral lobe showing greater androgen responsiveness than the dorsal or lateral lobes (45)(46)(47)(48). Additionally, AR expression is tightly regulated by androgens in the VP but is androgen-independent in the LP (49,50).…”