THE ANTIOXIDANT DEFENSES OF BRAIN MITOCHONDRIA DURING SHORT-TERM FOREBRAIN ISCHEMIA AND RECIRCULATION IN THE RAT

This study evaluated changes in the antioxidant defences of mitochondr ia induced by 30 min of forebrain ischemia and recirculation up to 24 h in rats. Following treatment, mitochondria were isolated from two br ain subregions: the dorsolateral striatum, an area in which there is l oss of most neurons, and the paramedian cortex in which most neurons a re resistant to damage. During ischemia and the first few hours of rec irculation, the mitochondrial defences were largely preserved based on measurements of the activities of the enzymes, superoxide dismutase, glutathione peroxidase and glutathione reductase, as well as the respo nse of the mitochondria to a subsequent exposure to H2O2 in vitro. How ever, some moderate changes were detected, particularly in the mitocho ndria from the dorsolateral striatum. A decrease of 30% in the activit y of superoxide dismutase was seen at the conclusion of the ischemic p eriod and a small increase in susceptibility to changes induced by H2O 2 was detected during early recirculation. This latter change preceded and possibly contributed to the development of an impairment of respi ratory function detected in mitochondria from the dorsolateral striatu m at 3 h of recirculation. At 24 h of recirculation, larger changes we re seen in the activities of all three of the enzymes in mitochondria from the dorsolateral striatum but not the paramedian cortex that was associated with progression to advanced neuronal damage in the former subregion. (C) 1998 Elsevier Science B.V. All rights reserved.