TY - JOUR T1 - Specificity of the <em>In Vitro</em> Destruction of Adrenal and Hepatic Microsomal Steroid Hydroxylases by Thiosteroids JF - Molecular Pharmacology JO - Mol Pharmacol SP - 997 LP - 1010 VL - 16 IS - 3 AU - R. H. MENARD AU - T. M. GUENTHNER AU - A. M. TABURET AU - H. KON AU - L. R. POHL AU - J. R. GILLETTE AU - H. V. GELBOIN AU - W. F. TRAGER Y1 - 1979/11/01 UR - http://molpharm.aspetjournals.org/content/16/3/997.abstract N2 - Studies are presented to show that thiosteroids such as deacetylspironolactone or 7α-thiotestosterone may be used as biochemical probes to correlate the amount of cytochrome P-450 associated with specific steroid hydroxylases. The ability of the thiosteroids to destroy cytochrome P-450 differed markedly among microsomes prepared from liver, adrenal and testicular tissues, and seemed proportional to the magnitude of the spectral interactions of the thiosteroids with cytochrome P-450. At low concentrations (1.0 µM), 7α-thiotestosterone caused a NADPH-dependent destruction of hepatic cytochrome P-450 which was associated with a preferential decrease in the activity of testosterone 7α-hydroxylase. At 4.5 µM, it also caused a NADPH-dependent decrease in 2β, 6β, and 16α-testosterone hydroxylase, but no NADPH-dependent decrease in benzo(a)pyrene hydroxylation. The destruction of adrenal cytochrome P-450 by deacetylspironolactone in guinea pig microsornes was concurrent with a decrease in the activity of progesterone 17α-hydroxylase, but not of progesterone 21-hydroxylase. Studies with radiolabeled deacetylspironolactone suggest that during the loss of cytochrome P-450 by thiosteroids the sulfur atom of the thio group after activation by cytochrome P-450 is eliminated from the steroid moiety and binds covalently to the cytochrome P-450-apoenzymes, thereby resulting in the concomitant loss of the activity and the heme of the cytochrome P-450-dependent steroid hydroxylase. ER -