Changes in endogenous antioxidant enzymes during cerebral ischemia and reperfusion

Objective: The purpose of this study was to investigate the role of catalase ( Cat), glutathione S transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx) in cerebral ischemia induced by occluding the carotid arteries of male Wistar rats. Methods: The activities of the antioxidant enzymes Cat, GR, GPx and GST were measured in the cerebral cortex, cerebellum and hippocampus regions after varying periods of ischemia and reperfusion. Results: In all ischemia/reperfusion groups (0, 1 and 24 hours of reperfusion), the enzyme activities were found to be altered when compared to the sham-operated controls. The alterations were significant (p <= 0.05) in all reperfusion groups, particularly after 1 hour of reperfusion in all brain regions; however, maximum alterations were detected in the more vulnerable hippocampus. Discussion: Our findings indicate that the endogenous antioxidant enzymes are activated as soon as 1 hour after ischemia. In spite of significant up-regulation of these enzymes, a large number of neurons in selectively vulnerable regions of hippocampus undergo neurodegeneration. These biochemical changes suggest that vulnerability to oxidative stress in brain is region-specific. However, these changes which are adaptive or compromise the capacity of the brain to deal with the oxidative stress that could lead to neurodegeneration remains to be understood.