Studies on the Destruction of Adrenal and Testicular Cytochrome P-450 by Spironolactone REQUIREMENT FOR THE 7n-THIO GROUP AND EVIDENCE FOR THE LOSS OF THE HEME AND APOPROTEINS

The administration of spironolactone, a diuretic steroid, is known to cause a depletion of microsomal cytochrome P-450 in those tissues which have a high activity of steroid 17a-hydroxylase. In this paper, studies are presented to indicate that the sulfur atom located at the carbon 7-a position on the spironolactone molecule is required for the loss of the heme and apoproteins of adrenal or testicular cytochrome P-450. In vitro studies revealed that losses in cytochrome P-450 could be caused by deacetylated spironolactone and to a lesser extent, by similar steroids that contained a 7~ methylthio or ‘la-methylsulfone group but not by steroids that lack these groups. The loss of cytochrome P450 by spironolactone in uivo paralleled a loss in the activity of progesterone 21and 17a-hydroxylase, and in the concentration of the heme of cytochrome P-450 measured either by the pyridine hemochromogen method or by EPR spectroscopy. Moreover, electrophoresis of adrenal microsomal proteins revealed decreases in the optical staining intensity of apoproteins of cytochrome P-450 after spironolactone treatment that paralleled the decrease in the amount of cytochrome P-450. In contrast, no loss in these bands occurred after the in vitro destruction of cytochrome P450 and its heme by deacetylspironolactone. The in viva or in vitro studies presented in this paper suggest that spironolactone or deacetylspironolactone may be converted by cytochrome P-450 (perhaps progesterone 17a-hydroxylase) to an active metabolite which, in turn, destroys the heme of cytochrome P-450, thereby decreasing steroid hydroxylase activities in the adrenal or in the testes.