EFFECT OF IMMOBILIZATION STRESS ON PLASMA LUTEINIZING-HORMONE, TESTOSTERONE, AND CORTICOSTERONE CONCENTRATIONS AND ON 3-BETA-HYDROXYSTEROIDDEHYDROGENASE-ACTIVITY IN THE TESTES OF ADULT-RATS

We have examined the effect of 3 hr of immobilization stress on plasma luteinizing hormone, testosterone, and corticosterone levels, and on the activity of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in mi crosomal and mitochondrial fractions of the testis from adult rats. Im mobilization for 3 hr increased plasma corticosterone and reduced plas ma testosterone concentrations by 57%. Plasma luteinizing hormone leve ls were lower, although not significantly (P = 0.093) so, in stressed animals. Immobilization (3 hr) reduced the V-max values of 3 beta-HSD in the mitochondria and in the microsomal fraction of the testis by 40 % and 34%, respectively, but had no effect on the K-m values of 3 beta -HSD in the two cellular compartments. These results suggest that the inhibition of the activity of 3 beta-HSD may be partially responsible for the disruption of testicular steroidogenesis during immobilization stress.