An in vitro cell model system to study the action of retinoids on Leydig cell steroidogenesis.

In this study we examined the effects of retinol and retinoic acid on steroid production in MA-10 mouse Leydig tumor cells. Results showed that both retinol and retinoic acid greatly increased progesterone production in this cloned cell line. The stimulatory effect of retinoids is not inhibited by cycloheximide suggesting that de novo protein synthesis is not required. The presence of the retinoid binding proteins CRBP and CRABP could not be detected in MA-10 Leydig cell cytosol indicating that the stimulatory action of retinoids on progesterone production is not mediated through these cellular binding proteins. Both previous and present findings suggest that retinoids play an important role in the regulation of Leydig cell steroidogenesis and that MA-10 Leydig tumor cells may represent an ideal in vitro cell system to study the mechanism of action of retinoids in Leydig cell steroidogenesis.