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

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.