Inhibition of Ca2+-dependent catecholamine release by myosin light chain kinase inhibitor, wortmannin, in adrenal chromaffin cells

Abstract To elucidate the possible involvement of myosin light chain kinase (MLCK) in the mechanism of exocytosis, we studied effects of MLCK inhibitor, wortmannin, on the secretory function of bovine adrenal chromaffin cells. Preincubation of chromaffin cells with wortmannin inhibited both acetylcholine- and high K + -evoked catecholamine (CA) release. The IC 50 for high K + -evoked CA release was 1μM. When the cells were permeabilized with digitonin after wortmannin preincubation, Ca 2+ -dependent exocytosis was inhibited in a dose-dependent manner (IC 50 , 1μM). These findings suggest the implication of MLCK in the Ca 2+ -triggered process in the machinery of exocytosis.