The role of cytochrome P-450 in the synthesis of polar metabolites of aldosterone by microsomes of male rat liver

Among the tissues of the male rat studied, the largest quantities of the neutral polar metabolites of aldosterone were synthesized by the hepatic microsomal fraction. The polar metabolites of aldosterone were separated by HPLC into six peaks. Three peaks of non-polar (reduced) metabolites were also synthesized. Synthesis of at least four of the neutral polar metabolites was induced by phenobarbital and inhibited by both CO and SKF-525A. The rates of synthesis of these metabolites, which were linear up to 5 minutes, correlated well with the concentration of cytochrome P-450 in the liver microsomes. Addition of aldosterone to the microsomal fraction caused a pronounced type 1 change in the cytochrome P-450 spectrum. The half maximal spectral change (K_s) for aldosterone was calculated to be 8 μM. These experiments indicate that the neutral polar metabolites of aldosterone are produced by cytochrome P-450 dependent hydroxy lations.