Substantial evidence indicates a role for reactive oxygen intermediates (ROIs) in postischemic reperfusion injury. Redox-active transition metals, such as iron and copper, are known to be involved in the production of ROIs. Using the rationale that zinc, a nonredox-active transition metal antagonizes endogenous copper and/or iron, a study is proposed to examine the cardioprotective effects of this metal in vitro and in vivo. Using a swine heart model and the isolated perfused rat heart, myocardial preservation will be examined by supplementing perfusion solutions with zinc-bis-histidial. Pig hearts will be subjected to global ischemia followed by 120 min of reperfusion. Rat hearts will be subjected to either 20 min of global ischemia or 10 min of regional ischemia. Cardiac functional states will be assessed by changes in left ventricular peak systolic and end diastolic pressures, plus/minus dp/dt and oxygen consumption. Total and catalytic copper will be determined in vitro and in vivo. Relationships between content of metals and severity of postischemic reperfusion injury will be assessed in isolated rat hearts preloaded with copper or iron and then subjected to normothermic global ischemia. To deplete copper, rats will be treated and D-Penicillamine. Membrane damage will be assessed by LDH and CK release. The ability of zinc to decrease the metal-enhanced damage will be tested. The second part of this project will assess the mechanisms that contribute to reperfusion induced oxidative stress. This portion is meant to complement the first part and will be conducted concurrently. Formation of OH and protein carbonyls will be determined in order to establish correlations between changes in cardiac transition metal content, radical formation, cardiac protein oxidation and severity of postischemic reperfusion injury. The last part of this project will examine from a mechanistic standpoint the interaction between copper and zinc using two models of copper-induced cardiac damage that have been characterized. By demonstrating that under certain controlled circumstances, zinc can be used to effectively prevent or decrease postischemic dysfunction period a new approach towards treatment or prevention of ROI-induced tissue injury may be identified.