Degradation of sarcolemmal phospholipids play a crucial role in the pathophysiology of myocardial reperfusion injury. Reperfusion of ischemic myocardium potentiates the intracellular signaling by alpha1-receptor stimulation through the phosphoinositide response generating putative second messengers, inositol phosphates and diglycerides, which are instrumental for Ca2+ release and protein kinase C activation, respectively. Activation of protein kinase C can initiate a cascade of adverse reactions for the heart. In addition, arachidonic acid released from phospholipids can cause intracellular Ca2+ overloading and generate free radicals via the microsomal respiratory chain. This proposed research will continue to explore the mechanisms of phospholipid breakdown in the ischemic reperfused myocardium by examining the intracellular signaling mechanisms of phospholipase D, alpha- adrenergic receptor and protein kinase C, as well as the membrane pathophysiology of phospholipid loss through cytochrome P-450 monooxygenase and ion channels. In addition, the role of ether-linked phospholipids (plasmalogens) will also be examined. The information obtained from our previous and proposed studies will be used to study the mechanism of gene expression, which will be used to develop therapeutic modalities to reduce reperfusion injury. mRNAs transcribed from genes expressed as a consequence of ischemia and reperfusion, and those resulting from phospholipid-dependent signaling will be identified by means of experimental interventions, and will used (gene therapy) to reduce reperfusion injury. The ultimate goal of this investigation is to develop drugs applicable to patient care for reduction of cellular injury associated with ischemia and reperfusion.