Sex difference in adrenal heme and cytochrome P-450 metabolism: evidence for the repressive regulatory role of testosterone

A novel aspect of the regulation of heme biosynthesis and cytochrome P450 concentration in rat adrenals, as pertains to the repressive role of testosterone, is described. Also, the pres-ence of a sex difference in the activities of #{244}-aminolevulinate (ALA) synthetase and heme oxygenase, as well as the concen-trations of heme and cytochrome P450 in the adrenal mitochon-dnal and the microsomal fractions, are defined. The female rats displayed a nearly 2-fold higher value for the listed parameters. Castration of rats caused an elevation of ALA synthetase activity to approximate that of the female rats, whereas testosterone replacement depressed the enzyme activity to the level of the sham-operated animals. Moreover, female rats treated with tes-tosterone showed a marked depreson in adrenal ALA synthe-tase aclivity. This was accompand by slgni#{241}cantreducbons in the mitochondrai and microsomal contents of cytochrome P-45