Mitochondrial inhibitors evoke catecholamine release from pheochromocytomacells

Quantal catecholamine secretion evoked from individual pheochromocytoma (PC 12) cells by exposure to mitochondrial inhibitors and uncouplers was monito red in real time using amperometry. Cyanide (0.05-5 mM) caused a concentrat ion-dependent increase in the frequency of amperometric events. This secret ory response was abolished by removal of extracellular Ca2+ and by the appl ication of Cd2+ (200 mu M), a nonselective blocker of voltage-gated Ca2+ ch annels. Secretion was also inhibited by ca. 75% following pretreatment of c ells with omega-conotoxin GVIA to inhibit N-type Ca2+ channels selectively. Secretion was also detected when cells were exposed to rotenone (10 mu M), dinitrophenol (250 mu M) and p-trifluoromethoxyphenyl hydrazone (1 mu M) a nd, as for cyanide, these secretory responses were abolished by removal of extracellular Ca2+ or application of 200 mu M Cd2+. These results indicate that, like hypoxia, mitochondrial inhibitors and uncouplers evoke catechola mine secretion from PC12 cells which is wholly dependent on Ca2+ influx thr ough voltage-gated Ca2+ channels. (C) 2000 Academic Press.