Abstract
The high concentration of Mg (high Mg) during hypoxia shows the protective effects on the cardiac hypoxia-reoxygenation injury. We examined the effects of high Mg on mitochondria. Male SD rat hearts were excised and perfused with Langendorff manner. After stabilization, heart was made hypoxic 30 min and reoxygenated 30 min. In control group, the Mg concentration is 1.2 mM and in high Mg group was 12 mM. The left ventricular developed pressure, heart rate and coronary perfusion pressure were monitored throughout the experiments. At the various timing of the experiment, perfusion was stopped and heart tissue was homogenized. The cytosol fraction was obtained by ultracentrifuge of homogenate and its cytochrome c and caspase-3 content were quantitated by Western blot analysis. In addition, mitochondrial ultrastructure was examined by electron microscopy. In high Mg group, the recovery level of pressure rate product by reoxygenation (30min; 80.3%±4.5 p<0.01 vs. control group) was significantly higher than that of control group (54.3%±4.5). Cytochrome c and caspase-3 content of cytosol were increased by reoxygenation, but the extent of the increase was significantly inhibited by high Mg during hypoxia. Mitochondria were swollen by hypoxia and incompletely recovered by reoxygenation. However, in high Mg group, the structure recovered to almost normal. These results suggest that high Mg during hypoxia protects mitochondria from cardiac hypoxia-reoxygenation injury, restrains apoptosis of the myocardium and facilitates the functional recovery of the hearts. [J Physiol Sci. 2007;57 Suppl:S204]
