Direct Inhibitory Effect of Estrogen on Leydig Cell Function of Hypophysectomized Rats

Abstract

The effects of estrogen upon testicular gonadotropin receptors and Leydig cell responses were studied. Immature hypophysectomized rats were treated for 7 days with 50 .mu.g FSH [follitropin], with or without diethylstilbestrol (DES). Daily injections of FSH induced a marked increase in testis weight; this wt increase was inhibited by concomitant DES treatment. FSH also induced an increase in testicular LH [lutropin]/hCG [human chorionic gonadotropin] receptor content; the increase in [125I]iodo-hCG binding was not affected by daily injections of low doses (0.01 and 0.2 .mu.g) of DES but was prevented by treatment with high doses (5 and 20 .mu.g) of DES. No significant change in testicular [125I]iodo-FSH-binding capacity was detected in any treatment group. Functional responses of the Leydig cells of hypophysectomized rats were studied by incubation of decapsulated testes with or without a saturating concentration of hCG. Daily treatment of FSH caused a marked increase in both basal and stimulated levels of testosterone production. DES treatment with or without concomitant FSH administration caused significant decreases in both basal and stimulated levels of testosterone production. The inhibitory effect of DES was shown to be dose-dependent, with 0.01 .mu.g DES showing significant inhibition. In contrast to the facilitatory effect of FSH upon testosterone production, a decrease in c[cyclic]AMP production was observed in FSH-treated animals; the inhibitory action of FSH was not affected by DES. A direct inhibitory effect of estrogen on steroidogenic responses was demonstrated in the Leydig cells of hypophysectomized immature rats. This was accompanied by a decrease in testicular wt and was partially correlated with a decrease in LH/hCG receptor content.