Effect of immobilization stress on plasma luteinizing hormone, testosterone, and corticosterone concentrations and on 3 beta-hydroxysteroid dehydrogenase 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 microsomal and mitochondrial fractions of the testis from adult rats. Immobilization for 3 hr increased plasma corticosterone and reduced plasma testosterone concentrations by 57%. Plasma luteinizing hormone levels were lower, although not significantly (P = 0.093) so, in stressed animals. Immobilization (3 hr) reduced the Vmax 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 Km 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.