Effect of extracellular Mg on ROS and Ca accumulation during reoxygenation of rat cardiomyocytes

Sharikabad, Mohammad N., Kirsten M. Østbye, Torstein Lyberg,and Odd Brørs. Effect of extracellular Mg on ROS and Ca accumulation during reoxygenation of rat cardiomyocytes. Am J Physiol Heart Circ Physiol 280: H344–H353, 2001.—The effects of Mg on reactive oxygen species (ROS) and cell Ca during reoxygenation of hypoxic rat cardiomyocytes were studied. Oxidation of 29,79-dichlorodihydrofluorescein (DCDHF) to dichlorofluorescein (DCF) and of dihydroethidium (DHE) to ethidium (ETH) within cells were used as markers for intracellular ROS levels and were determined by flow cytometry. DCDHF/DCF is sensitive to H2O2 and nitric oxide (NO), and DHE/ETH is sensitive to the superoxide anion (O2 z), respectively. Rapidly exchangeable cell Ca was determined by Ca uptake. Cells were exposed to hypoxia for 1 h and reoxygenation for 2 h. ROS levels, determined as DCF fluorescence, were increased 100–130% during reoxygenation alone and further increased 60% by increasing extracellular Mg concentration to 5 mM at reoxygenation. ROS levels, measured as ETH fluorescence, were increased 16–24% during reoxygenation but were not affected by Mg. Cell Ca increased threeto fourfold during reoxygenation. This increase was reduced 40% by 5 mM Mg, 57% by 10 mM 3,4-dichlorobenzamil (DCB) (inhibitor of Na/Ca exchange), and 75% by combining Mg and DCB. H2O2 (25 and 500 mM) reduced Ca 21