Prostaglandin F2α Regulation of LH-Stimulated Testosterone Production in Rat Testis1

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Abstract
The effect of PG[prostaglandin]F2.alpha. on testicular testosterone (T) production and its possible influence on LH [luteinizing hormone] action was studied in adult male rats in vivo and in vitro. Various doses of PGF2.alpha. were administered by slow infusion of 4 h duration, and plasma T was determined by radioimmunoassay in samples obtained through an indwelling cardiac catheter. PGF2.alpha. (250 .mu.g/rat) caused a rapid and consistent fall in plasma T to 50% of initial levels while during similar infusions of saline, plasma T increased by 60% on the average. PGE2 (250 .mu.g/rat) had no significant effect on plasma T. Infusion of anti-LH serum for 4 h reduced plasma T by 72%; infusion of 250 .mu.g/rat of PGF2.alpha. in anti-LH-treated rats did not reduce plasma further. LH administration (3 and 10, but not 1 mU/rat) overcame the PGF2.alpha.-induced drop in plasma T in a dose-dependent manner. Indomethacin treatment (1 or 2 mg/kg for 10 days) caused a significant and sustained elevation in plasma T. The basal T output by the decapsulated testis preparation in vitro was not affected by either PGF2.alpha., PGF2 (up to 10-3 and 10-4 M, respectively), anti-LH serum, or prostaglandin synthetase inhibitors, while the LH (25 mU/ml)-stimulated testosterone secretion was inhibited in a dose-dependent manner by PGF2.alpha. and its 15-methyl derivative (ED50 = 6.8 .times. 10-5 M) and was blocked by anti-LH. Prostaglandin synthetase inhibitors, indomethacin (10-6 M) and diclofenac-sodium (10-4 M), potentiated the stimulatory action of LH or hCG [human chorionic gonadotropin] in vitro; this was reversed by PGR2.alpha.. PGF2.alpha. apparently inhibits LH-stimulated testosterone production in Leydig cells. Since PGF2.alpha. production in the testis is stimulated by hCG or LH, endogenous PGF2.alpha. may act as a local regulator of LH action in the Leydig cells. The action of PGF2.alpha. on testicular steroidogenesis is thus analogous to its action on rat luteal cells and as in the female, PGF2.alpha. may be of physiological significance in testicular function in male rats.