Acute Immobilization Stress Disrupts Testicular Steroidogenesis in Adult Male Rats by Inhibiting the Activities of 17α‐Hydroxylase and 17,20‐Lyase Without Affecting the Binding of LH/hCG Receptors

Abstract

ABSTRACT: We have investigated the effect of acute immobilization (3 hours) stress on testicular steroidogenesis in the adult rat. Immobilization did not alter plasma luteinizing hormone (LH) levels, but plasma testosterone (T) levels were reduced by 82%. Plasma levels of corticosterone in stressed rats were elevated more than ninefold over control levels. After 3 hours of stress, testicular levels of progesterone were elevated 33%, and levels of 17α‐hydroxyprogesterone and T were reduced 47% and 37%, respectively, compared to controls. Immobilization for 3 hours had no effect on the association or dissociation rate constants of LH/human chorionic gonadotropin (hCG) receptors of testicular interstitial cells and did not alter specific hCG binding. The effect of 3 hours of immobilization on testicular 17α‐hydroxylase and 17,20‐lyase was assessed by incubating testicular microsomes from stressed and control animals in the presence of 21[ 14 C]progesterone and [ 3 H]17α‐hydroxypro‐gesterone. Immobilization of rats reduced the V Max values of 17α‐hydroxylase and 17,20‐tyase by 47% and 48%, respectively, but had no effect on the K m values. These results support the hypothesis that stress for 3 hours disrupts rat testicular steroidogenesis via a mechanism that is independent of changes in circulating levels of LH and the binding characteristics of LH/hCG receptors. The effects of immobilization on the content of testicular steroids and on the activities of 17α‐hydroxylase and 17,20‐lyase suggest that stress inhibits the activities of both 17α‐hydroxylase and 17,20‐lyase.