Effect of prolactin on the metabolism of androgens by the rat ventral prostate gland in vitro.

When homogenates of rat ventral prostate glands were incubated with varying amounts of prolactin (0.2, 0.8, or 2.0 IU per ml), there were significant alterations in the bioconversion of [3H]testosterone and its principal radiometabolites. A 2.0-IU per ml dose of prolactin significantly reduced the metabolism of labeled testosterone in the prostate gland (P less than or equal to 0.01). Similarly, the amounts of [3H]5alpha-androstane-3beta,-17beta-diol ([3H]androstanediol) formed from [3H]testosterone were significantly lower (P less than or equal to 0.05) in the prolactin-treated groups than they were in the controls. Only the highest dose of prolactin (namely, 2.0 IU per ml) impaired the conversion of [3H]testosterone to [3H]17beta-hydroxy-5alpha-androstan-3-one and to [3H]-dihydrotestosterone in the homogenates of rat ventral prostate glands. These findings suggest that prolactin is capable of exerting intracellular actions as evidenced by its ability to interfere with steroidogenesis in androgen-dependent tissues.