Experimental Studies of Hydroxyl Radical Generation in Reperfusion Injury after Cerebral Ischemia

ABSTRACT

The time course of hydroxyl radical generation in the brain and the intensity of brain hydroxyl radical(OH) generation were examined in rat during the first four hours after postischemia reperfusion. Hydroxyl radical production was measured using the salicylate trapping method in which the production of 2, 3-dihydroxybenzoic acid(DHBA) in hippocampus(CA1) 5 minutes after salicylate administration was used as an index of OH formation. The interstitial concentration changes of salicylate and 2, 3-DHBA were detected by intracerebral microdialysis following the intraperitoneal administration of salicylate(150mg/kg) using high pressure liquid chromatography-electrochemical(HPLC-EC) and -ultraviolet(-UV). Adult Sprague-Dawley rats were subjected to 20 minutes of bilateral carotid artery occlusion(BCAO) in either normotensive or hypotensive state. Serial changes of cerebral blood flow(CBF) were monitored by H2 clearance method. CBF of normotensive BCAO group(n=6) was found to be decreased only to 52% of baseline value, and OH production after reperfusion did not develop in this group. Rats in the BCAO hypotensive group(n=10) showed remarkable reduction of CBF to 27% of baseline(p<0.05) and 2~4 folds increase of 2, 3-DHBA/salicylate during the first 40 minutes of recirculation . Hydroxyl radical production in rats died(n=5) after the insult was significantly higher and lasted longer than that in rats survived(n=5)(p<0.05). Concentration of salicylate in perfusate increased during 100 minutes after the peritoneal injection and before reaching to a plateau, which lasted for 3 hours. The changes of cerebral tissue concentration of 2, 3-DHBA differed from those of salicylate. In 2, 3-DHBA, the plateau was reached rather slowly than that of salicylate and lasted for 2 hours. These data indicate that lobal cerebral ischemia could be induced by temporary BCAO only if the systemic hypotenion is accompanied, it can not be induced in normotensive group. The hydroxyl radical produced brain damage is prone to develop early in the reperfusion period and is correlated with the severity of ischemic insult.