In vitro conversion of cholesterol into aldosterone and cortisol in different zones of the bovine adrenal cortex.

The individual steps in the formation of aldosterone and cortisol from cholesterol were assayed in different subcellular preparations from the inner and outer zones of bovine adrenal cortex. In zona glomerulosa the 11 beta-, 18- and 21-hydroxylase activities were relatively high, whereas the 17 alpha-hydroxylase activity was relatively low. Cholesterol side-chain cleavage and 3 beta-hydroxysteroid-delta 5-oxidoreductase activity were similar in zona glomerulosa and zona fasciculata-reticularis. The differences were however only quantitative. In no case one specific fraction was totally devoid of enzyme activity. The total content of mitochondrial cytochrome P-450 was relatively high in zona fasciculata-reticularis whereas the content of microsomal cytochrome P-450 was similar in the two fractions. In view of the relatively small differences observed, it seems likely that other factors than distribution of the above enzymes are of major importance for the specific production of gluco- and mineralocorticoids in the two layers.