Depletion of cardiolipin and cytochrome c during ischemia increases hydrogen peroxide production from the electron transport chain

Mitochondrial electron transport is a major source of reactive oxygen species (ROS) during cardiac ischemia and reperfusion. In the isolated rabbit heart, 30 and 45 min of ischemia decrease the contents of cardiolipin and cytochrome c in subsarcolemmal mitochondria (SSM) located beneath the plasma membrane. In contrast, interfibrillar mitochondria (IFM) in the interior of the myocyte do not sustain a decrease in cardiolipin. We proposed that the depletion of cardiolipin and the accompanying cytochrome c loss during ischemia were critical events that amplified ROS production by mitochondria. The total production of H2O2 was measured in submitochondrial particles (SMP) prepared from rabbit heart SSM and IFM after 0, 15, 30, and 45 min of ischemia. With NADH as substrate, total H2O2 production was increased only in SMP from SSM after 30 and 45 min ischemia, when ischemia decreased the content of cardiolipin and cytochrome c. In contrast, ischemia did not augment H2O2 generation in SMP from IFM with preserved cardiolipin and cytochrome c content. Thus, during the evolution of ischemic injury, H2O2 production from the electron transport chain increased after depletion of cardiolipin and the loss of cytochrome c.