Corticosterone impairs the mRNA expression and activity of 3β- and 17β-hydroxysteroid dehydrogenases in adult rat Leydig cells

Abstract

Clinical and experimental studies, including our own observations, have shown the adverse effects of excess glucocorticoids on testicular steroid hormone production. The present study was designed to gain insight into the molecular mechanisms by which excess corticosterone impairs Leydig cell steroidogenesis. To achieve this, adult rats were administered with corticosterone-21-acetate (2 mg/100 g body weight) twice daily for 15 days. After the treatment period, rats were killed by decapitation. The testes were removed, decapsulated aseptically and used for the isolation of Leydig cells. Purified Leydig cells were used for assessing the activity of 3beta- and 17beta-hydroxysteroid dehydrogenases (HSDs) and total RNA isolation. For in vitro studies, purified Leydig cells (7.5 x 10(6) cells) of control rats were plated in culture flasks and exposed to different concentrations (50, 100, 200, 400, and 800 nmol/L) of corticosterone for 24 h. At the end of incubation, total RNA was isolated from cultured Leydig cells, and the mRNA of 3beta- and 17beta-HSDs was quantified by RT-PCR. A significant reduction in the activities and levels of 3beta-HSD type-I and 17beta-HSD type-III mRNAs in Leydig cells were observed. In vitro studies demonstrated a dose-dependent significant impairment in both the activity and mRNA expression of these enzymes. These results suggest that corticosterone might have a direct effect on the transcription of the genes of 3beta- and 17beta-HSD. It is inferred from the present in vivo and in vitro studies that one of the molecular mechanisms by which excess corticosterone decreases the steroidogenic potency of Leydig cells is by suppressing the mRNA expression of 3beta-HSD type-I and 17beta-HSD type-III enzymes.