[ESR study of free radical formation during ischemia-reperfusion injury in the rat brain and the protective effect of a new antioxidant].

By using the spin-trapping technique and electron spin resonance spectroscopy (ESR), we detected directly oxygen-derived free radicals in the brain exposed to ischemia and reperfusion. Forebrain ischemia was produced in the rat by bilateral occlusion of the common carotid arteries combined with hemorrhagic hypotension. The whole cerebral cortex was homogenized in the presence of the spin trap agent, N-tert-butyl-alpha-phenylnitrone, followed by a Folch extract. Spin-adducts were detected using ESR. As the index of tissue injury, the lipid peroxidation was estimated from both the amount of thiobarbituric acid reactive substance and the formation of conjugated diene. After 10 or 20 min of ischemia, reperfusion induced a burst of spin adduct formation which peaked at 5 min reperfusion time. The peak value increased with the ischemia time. The degree of lipid peroxidation, which was measured after 20 min of reperfusion, also increased with the ischemia time. When the oligomeric derivative was administered (9 mg . kg-1, i.p.) 30 min before ischemic insult, both spin adduct formation and lipid peroxidation were reduced. The results support the current view that free radicals produced upon reperfusion may be the direct cause of the subsequent lipid peroxidation.