| The activities of enzymes of platelet-activating factor (PAF) biosynthetic pathways were analyzed in hippocampal and cerebral cortical regions of normal and ischemic gerbil brain. Global forebrain ischemia was produced by bilateral carotid artery ligation, and the effectiveness of the ligation was assessed by free fatty acid release, ATP depletion, destruction of CA1 hippocampal neurons and intracardiac dye infusion. Specific activities of 1-alkyl-2-acetyl-sn-glycerol (AAG) choline phosphotransferase, 1-alkyl-sn-glycero-3-phosphate (AGP) acetyl transferase and 1-alkyl-sn-glycero-3-phosphocholine (lyso-PAF) acetyl transferase in tissue homogenates were in the ratio 3.5:1:0.1, respectively. Sham-operated and ischemic or ischemic-reperfused tissues showed similar activities for individual enzymes. Physiological concentrations of MgATP severely inhibited AGP acetyl transferase activity suggesting that falling ATP levels in cerebral ischemia may promote the de novo pathway of PAF biosynthesis. The effects of other small metabolites on the activities of enzymes in the PAF biosynthetic pathway were also examined. |
