Mitochondrial depolarization accompanies cytochrome c release during apoptosis in PC6 cells

Cytochrome c is released from mitochondria into the cytosol in cells underg oing apoptosis. The temporal relationship between cytochrome c release and loss of mitochondrial membrane potential was monitored by laser-scanning co nfocal microscopy in single living pheochromocytoma-6 cells undergoing apop tosis induced by staurosporine. Mitochondrial membrane potential monitored by tetramethylrhodamine methyl ester decreased abruptly in individual cells from 2 to 7 h after treatment with staurosporine. Depolarization was accom panied by cytochrome c release documented by release of transfected green f luorescent protein-tagged cytochrome c in these cells. The results show tha t mitochondrial depolarization accompanies cytochrome c release in pheochro mocytoma-6 cells undergoing apoptosis.