ACUTE IMMOBILIZATION STRESS DISRUPTS TESTICULAR STEROIDOGENESIS IN ADULT MALE-RATS BY INHIBITING THE ACTIVITIES OF 17-ALPHA-HYDROXYLASE AND17,20-LYASE WITHOUT AFFECTING THE BINDING OF LH HCG RECEPTORS/

We have investigated the effect of acute immobilization (3 hours) stre ss on testicular steroidogenesis in the adult rat. Immobilization did not alter plasma luteinizing hormone (LH) levels, but plasma testoster one (T) levels were reduced by 82%. Plasma levels of corticosterone in stressed rats were elevated more than ninefold over control levels. A fter 3 hours of stress, testicular levels of progesterone were elevate d 33%, and levels of 17 alpha-hydroxyprogesterone and T were reduced 4 7% and 37%, respectively, compared to controls. Immobilization for 3 h ours had no effect on the association or dissociation rate constants o f LH/human chorionic gonadotropin (hCG) receptors of testicular inters titial cells and did not alter specific hCG binding. The effect of 3 h ours of immobilization on testicular 17 alpha-hydroxylase and 17,20-ly ase was assessed by incubating testicular microsomes from stressed and control animals in the presence of 21[C-14]progesterone and [H-3]17 a lpha-hydroxyprogesterone. Immobilization of rats reduced the V-max val ues of 17 alpha-hydroxylase and 17,20-lyase by 47% and 48%, respective ly, but had no effect on the K-m values. These results support the hyp othesis that stress for 3 hours disrupts rat testicular steroidogenesi s via a mechanism that is independent of changes in circulating levels of LH and the binding characteristics of LH/hCG receptors. The effect s of immobilization on the content of testicular steroids and on the a ctivities of 17 alpha-hydroxylase and 17,20-lyase suggest that stress inhibits the activities of both 17 alpha-hydroxylase and 17,20-lyase.