Effect of Anti-Oxidants on Lipid Oxidation After Hypoxic Ischemic Brain Injury in Piglets † 1878

Abstract

Free radicals are important moderators of hypoxic ischemic brain injury in newborn rodents but may be less important in more advanced species. 0 to 3 day old piglets were subjected to hypoxic ishcemic brain injury. Drug or vehicle were given at -15 minutes. At time 0 carotid arteries were clamped and blood was withdrawn to reduce the blood pressure to 67% of normal. At 15 minutes inspired oxygen was reduced to 6%. At 30 minutes the carotid clamps were released, the blood was reinfused and the oxygen was switched to 100%. Brains were frozen in situ in liquid nitrogen and removed at various times after reoxygenation. Samples of cerebral cortex were homogenized in ice cold buffer. Thiobarbituric acid reative substance (TBARS), oxidized to reduced glutathione ratio(GSSG/GSH) and Na,K ATPase were measured. Brain TBARS is increased at 30 minutes after reoxygenation relative to sham piglets but not at 15, 60, 90,or 120 minutes. GSSG/GSH peaks at 30 minutes and remains elevated to 120 minutes. Na, K ATPase does not change with hypoxic ischemia and reperfusion. The increase in TBARS at 30 min after reoxygenation (154±29 SE pmol/g shams to 429±64, after hypoxic ischemic injury, p<.01) is reduced by 100 mg/kg deferoximine (to 232±22, p<.05 relative to hypoxic ischemia alone),by 200 mg/kg vitamin E (to 286±44, p<.05),or by 20 mg/kg (to 214±22, p<.05)but not lower doses of U-74389G (desmethyl trilizad). TBARS after injury are three orders of magnitude lower than in rodents. The increase in GSSG/GSH (33±1% shams to 44±3% hypoxic ischemia and 30 minutes reoxygenation, p<.01) was not effected by any of the drugs(45±3% deferoximine,48±3% vitamin E,and 45±3% U-74389G). In vitro the increase in TBARS caused by incubating homogenized brain with 0.5 to 2 umol/g of superoxide is prevented by EDTA suggesting iron dependent hydroxyradical involvement. The increase in GSSG/GSH caused by incubating homogenized brain with superoxide is not effected by EDTA and thus is not caused by iron dependent hydroxyradical. Ischemia reperfusion produces lipid oxidation in the piglet that is partially inhibitable by anti-oxidants. In vitro responces suggest that only the hydroxyradical dependent portion is inhibitable by these agents.