Sites of Action of -Melanocyte Stimulating Hormone in Aldosterone Biosynthesis in the Rat

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Abstract
The sites of action of .beta.-melanocyte stimulating hormone (.beta.-MSH) on aldosterone biosynthesis were studied using collagenase-dispersed adrenal glomerulosa cells from rats maintained on either normal or Na-deficient diets for 2 wk. Isolated cells were treated with a cyanoketone derivative (WIN 19,578) to isolate the early and late steps in aldosterone biosynthesis. WIN 19,578 (1 .mu.M) completely blocked aldosterone production stimulated by Na depletion, AII, ACTH and .beta.-MSH, .beta.-MSH (1 .mu.M) significantly stimulated pregnenolone production (early step) and the conversion of corticosterone to aldosterone (late step) in aldosterone biosynthesis. The effect of .beta.-MSH was similar to AII and ACTH. Na depletion enhanced the effect of .beta.-MSH only on the late step in aldosterone biosynthesis. .beta.-MSH stimulates both the early and late steps of aldosterone biosynthesis. .beta.-MSH or peptides containing .beta.-MSH may play a role in the regulation of aldosterone production.