SWELLING-INDUCED CATECHOLAMINE SECRETION RECORDED FROM SINGLE CHROMAFFIN CELLS

We have studied osmotically induced catecholamine secretion from bovin e adrenal chromaffin cells by combining patch-damp measurements, elect rochemical detection of secretion, and Fura-2. measurements of intrace llular free calcium concentration ([Ca2+](i)). We find that osmoticall y induced catecholamine release is exocytotic and calcium dependent. F urthermore, we demonstrate that cell swelling is coupled to such secre tion via a volume-activated current, carrying predominantly chloride, which causes a plateau depolarization of the cell membrane potential a nd thus promotes voltage-activated calcium influx. Therefore, cell vol ume changes may modulate the secretory activity.