The effects of temperature on the activity of testicular steroidogenic enzymes

Decreased sperm counts and impaired sperm motility are present in a substantial proportion of men with varicocele. Elevations in the temperature of the affected testis, and increased spermatic vein estra-diol (E 2) concentrations have been found in some of these patients. To investigate the possibility that increases in temperature lead to a pattern of testicular steroidogenesis that results in increased E 2 synthesis, we have examined the effects of temperature changes on the activities of four important testicular steroidogenic enzymes. 3-β-hydroxysteroid dehydrogenase (3β-HSD), 17-hydroxylase (17-OH), 17, 20-desmolase (17, 20-D) and aromatase activities were measured in the microsomal fraction of rat, pig and horse testes. Incubations were performed at 34°C, 36°C, and 38°C. The activities of all 4 enzymes increased with each 2°C temperature elevation in roughly proportional amounts. We conclude that minor elevations in incubation temperature are associated with increases in the in vitro activity of four key testicular steroidogenic enzymes.