The participation of cAMP and protein kinase C in the regulation of aldosterone biosynthesis by potassium.

The mechanism of the effect of potassium ions (K+) on aldosterone production in guinea pig adrenal cortex was examined. At high K+ concentrations (approximately 8 mM) in the incubation media, aldosterone output and content was elevated, and there was a significant increase in the phosphorylation of intracellular proteins and of protein kinase C activity. Cyclic AMP levels showed a less significant increase. EGTA and lanthanum ions (La3+), and also chlorpromazine with regard to protein phosphorylation, appeared to remove the effect of raised K+ concentrations on steroidogenesis and protein phosphorylation. At low K+ concentrations, addition of EGTA led to a significant accumulation of cyclic AMP. Evidence that steroidogenesis is regulated by a cyclic-AMP-dependent mechanism at low K+ levels is presented, and we also report the first direct evidence of activation of aldosterone synthesis by protein kinase C at high K+ concentration.