Abstract
Abstract
The biosynthesis of 18-hydroxycortisol and 18-oxocortisol from cortisol was studied in calf adrenal zona glomerulosa mitochondria. Cortisol is converted to 18-hydroxycortisol and 18-oxocortisol in the same mitochondrial preparation in which corticosterone is metabolized to 18-hydroxycorticosterone and aldosterone. Cortisol and 18-hydroxycortisol interacted with mitochondria to cause a Type I differential spectrum, which was decreased by sodium dithionite. The metabolism of cortisol to 18-hydroxycortisol and 18-oxocortisol was inhibited by metyrapone in a competitive way.
Cortisol was a competitive inhibitor of the transformation of corticosterone into 18-hydroxycorticosterone and aldosterone, and corticosterone was a competitive inhibitor of the transformation of cortisol into 18-hydroxycortisol and 18-oxocortisol, with a <Ki very similar to the <Km for the transformation of that steroid to aldosterone. These results indicate that cotisol is metabolized to 18-hydroxycortisol and 18-oxocortisol by a mitochondrial cytochrome P-450, which is the same as that which catalyzes the conversion of corticosterone into aldosterone.
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