Accelerated phospholipid catabolism is an important contributor to electrophysiologic dysfunction and cell death in ischemic myocardium. Although many of the pathophysiologic sequelae of myocardial ischemia are likely mediated by accelerated sarcolemmal phospholipid hydrolysis and plasmalogens are the major phospholipid constituents of sarcolemma, alterations in plasmalogen catabolism during myocardial ischemia have been virtually ignored. Similarly the role of plasmalogens and their catabolites as specific lipid mediators of agonist stimulation in myocardium has not been examined. Accordingly, the magnitude and temporal course of alterations in plasmalogen catabolism during ischemia and agonist stimulation will be quantified utilizing pulse chase labeling techniques and the enzymic mediators responsible for these alterations (e.g. phospholipases A2, C, and D or plasmalogenase) will be identified. Since accelerated sarcolemmal phospholipid metabolism has never been directly demonstrated, alterations in the sarcolemmal compartment during anoxia and agonist stimulation will be assessed by specifically incorporating radiolabeled plasmalogens and diacyl phospholipids into the sarcolemma of intact myocytes utilizing phospholipid exchange protein. The synergistic, additive or protective effects of agonist stimulation or antagonist attentuation of ischemia induced alterations in myocardial plasmalogen catabolism will be determined. The physiologic sequelae of altered myocardial plasmalogen metabolism will be investigated by purification of individual isoforms of protein kinase C and identification of isoforms which are selectively activated by ether-linked diglycerides. Specific alterations in membrane molecular dynamics and ion transport kinetics induced by plasmalogen catabolites will be delineated. Taken together, the proposed research will be the first systematic investigation of alterations in the catabolism of the predominant phospholipid constituents of myocardial sarcolemma during ischemia and agonist stimulation and will specifically identify the importance of plasmalogen catabolites as activators of protein kinase C and modulators of membrane molecular dynamic and ion flux.
