目的和方法：用ＡＣＡＳ５７０粘附式细胞仪，以荧光素染色法观察镁（Ｍｇ２＋）对体外培养乳鼠心肌细胞内游离钙（Ｃａ２＋）的影响及对缺氧再给氧时细胞内Ｃａ２＋作用。结果：细胞外Ｍｇ２＋降至０３ｍｍｏｌ·Ｌ－１，细胞内Ｃａ２＋荧光强度上升速度加快，达到稳定所需时间延长，出现Ｃａ２＋振荡曲线。增加Ｍｇ２＋浓度可使细胞内Ｃａ２＋降低。Ｍｇ２＋还可以显著减少缺氧再给氧时细胞内Ｃａ２＋，Ｐ＜００１。结论：细胞外低Ｍｇ２＋可导致细胞内Ｃａ２＋增加，Ｍｇ２＋有维持正常心肌细胞内Ｃａ２＋稳定性及拮抗缺氧再给氧时细胞内Ｃａ２＋超载作用 PURPOSE AND METHODS: The effects of magnesium (Mg2 +) on intracellular free calcium (Ca2 +) in neonatal rat cardiomyocytes and the effect of intracellular Ca2 + on hypoxia-reoxygenation were observed by ACAS570 adherent cytometer. Results: The extracellular Mg2 + decreased to 03 mmol·L-1, the intracellular Ca2 + fluorescence intensity increased faster, reaching the time required for stabilization, Ca2 oscillations appeared. Increasing the concentration of Mg2 + can decrease intracellular Ca2 +. Mg2 + also significantly reduced intracellular Ca2 + during hypoxia-reoxygenation, P <001. CONCLUSION: Extracellular low Mg2 + can lead to an increase of intracellular Ca2 +, Mg2 + can maintain the stability of intracellular Ca2 + in normal cardiomyocytes and antagonize the intracellular Ca2 + overload in hypoxia-reoxygenation