Inhibition of corticosteroid 11β hydroxylation in bovine zona fasciculata cells by the potassium entry blocker 4-aminopyridine

Abstract The potassium entry blocker, 4-aminopyridine has been used to evaluate the importance of this cation in several tissues including the adrenal cortex [4]. Since it inhibited corticosteroidogenesis, an important role for potassium entry in the control of this process has been implied. In the present in vitro study, 4-aminopyridine inhibited cortisol and corticosterone production and, at high concentrations, that of 11-deoxycortisol and 11-deoxycorticosterone. However, at lower concentrations, 11-deoxy-corticosteroid production increased suggesting that 4-aminopyridine acts as an inhibitor of 11β hydroxylation. Its slight resemblance to metyrapone may suggest that it acts, at least in part, by competing for cytochrome P450. However, its use as a potassium inhibitor in studies of the adrenal cortex may give ambiguous results.