Mitochondrial superoxide anion radicals mediate induction of apoptosis in cardiac myoblasts exposed to chronic hypoxia

► Hypoxia triggers accumulation of oxidised proteins within 30 min and necrosis. ► Chronic hypoxia (4 h) promotes mitochondrial ROS production and apoptosis. ► Inhibition of respiratory chain prevents hypoxia-induced ROS and apoptosis at 4 h. ► Hypoxia-induced necrosis after 30 min is not mediated by mitochondrial ROS.