Immunochemical evidence for exocytosis in isolated chromaffin cells after stimulation with depolarizing agents

After chemical stimulation with depolarizing agents (Ba2+ or Ca2+/carbachol) isolated living chromaffin cells display a drastically increased binding capacity for anti-DBH, distributed spotwise on or near the outer cell membrane. This effect is inhibited by noradrenaline; it is not evoked by the non-exocytotically releasing agents tyramine and reserpine. the effect of apparent externalization of DBH is paralleled by the observation of a DBH-dependent binding of 125I-labelled protein A upon the same depolarizing stimuli. These observations are discussed as possible evidence for exocytotic activities.