Oxidative stress during hypoxia in isolated-perfused rat heart.

These data suggest that oxidative stress occurs at the low oxygen tensions which exist during perfusion of rat heart tissue with hypoxic medium. Importantly, no evidence was found for additional oxidative injury after 4 min reoxygenation when enzyme release is maximal in this system suggesting the oxygen paradox is unrelated to oxidative stress. However, the oxidative changes evident after 10-15 min of hypoxia do support the occurrence of free radical mediated injury at low oxygen tensions, and it is possible this injury is involved in the changes which lead to cell lysis at reoxygenation. The source of this oxidative stress is not known, but appears to be greater in mitochondria and may arise from an increased production of reactive oxygen species by this organelle. Whether the observed oxidative changes are directly injurious to a cell is not yet clear.