Direct Inhibitory Effect of Glucocorticoids upon Testicular Luteinizing Hormone Receptor and Steroidogenesis in Vivo and in Vitro

The direct effects of glucocorticoids on testicular LH receptor content and steroidogenesis were studied in vivo and in vitro. Immature hypophysectomized rats were treated with varying doses of dexamethasone, corticosterone, or a synthetic progestin, 17,21-dimethyl-19-nor-pregna-4,9-diene-3,20-dione (R5020). Some animals were also treated concomitantly with FSH to prevent the hypophysectomy-induced decrease in testis functions. At the end of 5 days of treatment, testicular LH/hCG receptor content was measured by [¹²⁵I]hCG binding assay while steroidogenic responsiveness was measured by in vitro incubation of testes. Dexamethasone decreased testicular LH receptor in control and FSH-treated hypophysectomized rats in doses as low as 10 μg/day, whereas corticosterone (10 μg/day) decreased testicular LH receptor in the FSH-treated rats but had no effect in rats not treated with FSH. In contrast, R5020 had no effect on testicular LH receptor content. In vivo treatment of hypophysectomized rats with FSH increased both basal and hCG-stimulated production of androstanediol in vitro. In contrast, concomitant treatment with dexamethasone, but not R5020, decreased both basal and hCG-stimulated testicular androstanediol production. The direct effect of glucocorticoids on testicular steroidogenic potentials was also studied in primary culture of testicular cells obtained from adult hypophysectomized rats. Treatment of cultured testicular cells with hCG increased testosterone production. The addition of various natural and synthetic glucocorticoids, but not R5020, to hCGtreated cells decreased testosterone production in a dose- and time-related manner (triamcinolone ≤ dexamethasone > cortisol ≤ corticosterone). A 40% decrease in testosterone production was apparent at 6 h after addition of 10^-7 M dexamethasone to hCG-treated cells. These results demonstrate the direct inhibitory effect of glucocorticoids on testicular LH receptor content and steroidogenesis, suggesting the adrenal glucocorticoids may regulate testis functions.