Dose-dependent effects of human prolactin on the immature hypophysectomized rat testis.

We have studied dose-dependent effects of highly purified human PRL (39 IU/mg) on the testis of immature (22-day-old) hypophysectomized rats daily supplemented for 7 days with 2, 10, or 30 micrograms hormone. Dose-dependent stimulation was observed for all parameters: testis weight (1.6- and 2-fold above control for 10 and 30 micrograms PRL), basal and hCG-stimulated testosterone (14- and 21-fold), intratesticular testosterone (7- and 21-fold) and estradiol (1.2- and 1.5-fold), LH receptor concentration (1.8- and 2.5-fold), in vitro pregnenolone production by cholesterol side-chain cleavage enzyme (3-, 5- and 7-fold), and aromatase activity (2.1- and 2.4-fold). The number of Leydig cells exhibiting immunoreactivity toward anti-P450scc, anti-P450(17 alpha), and anti-3 beta-hydroxysteroid dehydrogenase antibodies also underwent a dose-dependent increase (under conditions revealing many immunopositive cells in hypox control animals). The respective increases were 8- to 14-fold for anti-P450scc and P450(17 al...