Background: This study investigated the effects of ischemic preconditioning on myocardial carnitine-linked metabolism and high-energy phosphates in the canine model of ischemia and reperfusion.
Methods: Anesthetized dogs underwent 1 hour of coronary artery occlusion and 4.5 hours of reperfusion. The dogs were randomly assigned to a control group (no intervention for 30 minutes), a preconditioned group (four repeated episodes of 3 minutes of mechanical coronary occlusion, each followed by 5 minutes of reperfusion), and a coronary cyclic flow variation (CFV) group (coronary artery stenosis and endothelial injury, resulting in an average of four episodes of platelet thrombosis and dislodgment). After completion of the protocol, ATP, creatine phosphate, and long-chain acyl carnitine concentrations were studied in both nonischemic and previously ischemic myocardium.
Results: In Part I of this study (Ovize et al., Circulation 1992, 85:779-789), it was reported that both mechanical occlusion and CFV before sustained occlusion resulted in a decrease in infarct size. In the present paper, we report changes in high-energy phosphates and long-chain acyl carnitine in these groups. Control, preconditioned, and CFV groups showed similar depletion in ATP content and "overshoot" in creatine phosphate stores. Control dogs exhibited a significant accumulation of long-chain acyl carnitine in the previously ischemic tissue (219 +/- 61 vs 131 +/- 38 nmoles/g wet weight in the nonischemic tissue; P < 0.05). No significant increase in long-chain acyl carnitine occurred in the mechanically preconditioned and CFV groups.
Conclusions: These results indicate that brief episodes of transient ischemia before sustained coronary occlusion prevent long-chain acyl carnitine accumulation in the ischemic and reperfused canine myocardium.