Effects of beta-lipotropin, beta-endorphin, gamma 2-melanotropin and corticotropin on steroid production by isolated human adrenocortical cells.

Normal human adrenocortical cells (from multi-organ donors) were incubated with corticotropin (tetracosactide), highly purified human beta-lipotropin, synthetic human beta-lipotropin, gamma 2-melanocyte stimulating hormone and beta-endorphin. Corticotropin stimulated cortisol, aldosterone and 18-hydroxycorticosterone production starting at 10(-12)-10(-11) mol/l in normal adrenocortical cells. Purified human beta-lipotropin also stimulated steroidogenesis but 100-1000-fold higher concentrations of the peptide were needed. In contrast, synthetic human beta-lipotropin was without any effect on steroid production up to concentrations of 10(-7) mol/l. Synthetic beta-lipotropin (5 x 10(-10) mol/l) did not significantly change the dose-response curve for corticotropin (10(-13) mol/l-10(-9) mol/l) versus the three steroids measured. gamma 2-Melanotropin and beta-endorphin (10(-6) mol/l) stimulated the secretion of cortisol, but not of aldosterone. Since synthetic human beta-lipotropin has no effect on human adrenocortical cells, the purified beta-lipotropin must be contaminated with traces of corticotropin. Since pathologically elevated levels of proopiomelanocortin-derived peptides will rarely exceed plasma concentrations of 10(-10) mol/l, our findings in vitro do not support a physiological or pathophysiological role of the peptides examined in the regulation of adrenal steroid secretion.