The antioxidant defences of brain mitochondria during short-term forebrain ischemia and recirculation in the rat

This study evaluated changes in the antioxidant defences of mitochondria induced by 30 min of forebrain ischemia and recirculation up to 24 h in rats. Following treatment, mitochondria were isolated from two brain subregions: the dorsolateral striatum, an area in which there is loss of most neurons, and the paramedian cortex in which most neurons are resistant to damage. During ischemia and the first few hours of recirculation, 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 response of the mitochondria to a subsequent exposure to H₂O₂ in vitro. However, some moderate changes were detected, particularly in the mitochondria from the dorsolateral striatum. A decrease of 30% in the activity of superoxide dismutase was seen at the conclusion of the ischemic period and a small increase in susceptibility to changes induced by H₂O₂ was detected during early recirculation. This latter change preceded and possibly contributed to the development of an impairment of respiratory function detected in mitochondria from the dorsolateral striatum at 3 h of recirculation. At 24 h of recirculation, larger changes were 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.