Abstract
The high concentration of Mg (HMg) during hypoxia or ischemic post-conditioning (IPT) shows the protective effects on the cardiac hypoxia-reoxygenation injury. We examined if the combination of HMg with IPT (HMg+IPT) potentiates the protective effects on the cardiac hypoxia-reoxygenation injury. Male SD rat hearts were excised and perfused with Langendorff manner. After stabilization, heart was made hypoxic for 45 min and reoxygenated for 30 min. In control, the Mg concentration was 1.2 mM and in HMg group it was 6 mM during hypoxia. IPT was 3 cycles of 10 sec ischemia and 10 sec reperfusion before reoxygenation. The left ventricular developed pressure and heart rate were monitored throughout the experiments. At various timing of the experiment, perfusion was stopped and heart tissue was fixed to examine mitochondrial ultrastructure by electron microscopy. In HMg and IPT groups, the recovery levels of pressure rate product (%PRP) by reoxygenation were higher than that of control group. In HMg+IPT group,%PRP was significantly higher than that of HMg, IPT and control group. Mitochondria were swollen by hypoxia and incompletely recovered by reoxygenation. However, in HMg, IPT and HMg+IPT groups, the structure recovered to almost normal. These results suggest that HMg during hypoxia with IPT potentiate protective effects on myocardium and facilitates the functional recovery of the hearts. [J Physiol Sci. 2008;58 Suppl:S186]
