Ischemic preconditioning diminishes oxygen demand and increases coronary flow in the early phase of reperfusion in rat heart

摘要

SUMMARYBackground: Ischemic preconditioning (IPC) can be defined as an adaptive mechanism induced by a brief period of reversible ischemia increasing the heart’s resistance to a subsequent longer period ofischemia. The objective of our research was to describe the effects of IPC on the hemodynamic function and metabolism of the myocardium during postischemic reperfusion.Material/Methods: 20 rat hearts were assigned to a preconditioning group (n=10) or to a control group (n=10). Preconditioning was achieved with 5 min. of global ischemia and 10 min. of reperfusion followed by 40 min. of ischemia. We investigated the postischemic recovery of aortic pressure, cardiac output, and coronary flow, as well as oxygen consumption, carbon dioxide release, and [H+] release.Results: No significant intergroup differences in aortic pressure and cardiac output were observed during reperfusion. In both groups, increased coronary flow (greater in the IPC group: 11.4±0.6 ml/min. vs 9.1±0.5 ml/min. in control group) was observed in the early phase of reperfusion. This was accompanied by a rise in CO2 and [H+] release, which was also greater in the IPC group. Oxygen consumption was significantly lower in the IPC group in the laterphase of reperfusion (9.39±0.53 vs 11.79±0.54 µmol/min/g dry weight), as were CO2 and [H+] release.Conclusions: IPC diminishes oxygen demand during reperfusion without changing the hemodynamic function considerably. IPC results in a transient increase of coronary flow accompanied by a rise in CO2 and [H+] release.