Inhibition of hCG- and cAMP-stimulated progesterone production in MA-10 mouse Leydig tumor cells by ketoconazole

In this study we attempted to examine the effects of ketoconazole on steroid biosynthesis and to determine which steps in the steroidogenic pathway were blocked using MA-10 Mouse Leydig tumor cells. This cloned cell line produces progesterone as the major steroid following stimulation by hCG or dbcAMP. At a concentration of 1 microM ketoconazole completely inhibited the hCG- and dbcAMP-stimulated progesterone synthesis in MA-10 Leydig cells. The conversion of 25-hydroxycholesterol and 22R-hydroxycholesterol into progesterone was also suppressed by this drug. The presence of ketoconazole inhibited mitochondrial steroid synthesis but required high concentrations of the drug as compared to inhibition in intact cells. No accumulation of pregnenolone was observed in the presence of ketoconazole indicating that the activity of 3 beta-hydroxysteroid dehydrogenase was not affected. We conclude that ketoconazole directly inhibits the activity of cholesterol side-chain cleavage enzyme (CSCC), a rate-determining enzymatic step in steroidogenesis, by interacting with cytochrome P-450scc.