A study on the optimal ions compostion in hyperkalemic cardioplegic solution in each growth stage

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The effects of calsium (Ca) and magnesium (Mg) ions in cardioplegic solutions on intracellular calcium ion handling and cardioprotection during hypoxia and reoxygenation which simulated ischemia and reperfusion or during the arrest of contraction and recontraction under aerobic condition were investigated in cultured neonatal rat myocardial cells.1. When Mg was not included in the cardioplegic solutions, the intracellular Ca concentration increased during hypoxia and reoxygenation and brought cell injury in ischemia model.2. The increase in intracellular Ca concentration during hypoxia and reoxygenation was suppressed by the addition of Mg independent of cardioplegic Ca concentration.3. However, the perfusion of the low Ca cardioplegic solution in which the Mg concentration was high increased intracellular Ca concentration and cell injury during reoxygenation.4. The intracellular Ca concentration increased during recontraction only in the low Ca cardioplegic solution without Mg and did not increase in the other Ca and Mg concentrations under aerobic condition. The findings suggest that in immature myocardium, the concentrations of Ca and Mg present in cardioplegic solutions influence intracellular Ca handling and cardioprotective effect.