Background:Reactive oxygen species (ROS) have been suggested to be involved in cellular damage caused by ischemia-reperfusion, anoxia-reperfusion, and hypoxia-reperfusion. We previously demonstrated that the generation of ROS was enhanced following hypoxia caused by an increased oxygen demand, and this was related to a shift in the tissue redox balance toward reduction. The aim of the present study was to elucidate the relationship among changes in ROS generation, tissue pO 2 levels, and redox balance changes in brain slices following hypoxia caused by a decreased oxygen supply. MethodsWe measured ROS-dependent chemiluminescence in cerebral cortex slices using a photonic imaging method as well as tissue pO 2 levels and the redox balance using micro sensors during reoxygenation after hypoxia caused by the deprivation of an adequate oxygen supply. ResultsROS-dependent chemiluminescent intensity was transiently enhanced during reoxygenation after the hypoxic treatment. Tissue pO 2 levels decreased and the tissue redox balance shifted towards reduction with the hypoxic treatment, followed by restoration to the steady-state condition. Increased ROS generation following hypoxia was related to a transient decrease in tissue pO 2 levels and a shift in the tissue redox balance towards reduction. ConclusionsThe present results demonstrated that ROS generation increased following hypoxia caused by a decreased oxygen supply. In addition, a transient redox shift to "hyper-reduction" with pO 2 changes may be involved in ROS generation in tissue.

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