Action of phospholipases A2 and C on free fatty acid release during complete ischemia in rat neocortex

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Abstract
The levels of brain free fatty acids rapidly increase after the onset of ischemia. The purpose of this study was to investigate the action of phospholipases A2 and C during complete ischemia based on the effects of a phospholipase C inhibitor (phenylmethylsulfonyl fluoride) and the N-methyl-D-aspartate antagonist MK-801 on the release of free fatty acids in rat neocortex. Complete brain ischemia was induced in rats with cardiac arrest by intracardiac injection of KCl. Free fatty acid levels in the neocortex were measured 0, 2, 4, and 8 minutes after cardiac arrest. Phenylmethylsulfonyl fluoride inhibited the release of free fatty acids primarily from phosphatidylinositol during the first 2 minutes of ischemia and from phosphatidylcholine and phosphatidylethanolamine at 4 to 8 minutes of ischemia. Conversely, MK-801 inhibited free fatty acid release mainly from phosphatidylcholine and phosphatidylethanolamine at 2 to 4 minutes of ischemia. These results indicate that the release of free fatty acids during the first 2 minutes of ischemia can be attributed mostly to the action of phospholipase C, and that the activation of phospholipase C further influences the activation of phospholipase A2 in the subsequent course, while phospholipase A2 predominantly acts after 2 minutes of ischemia.