Effect of hydrogen peroxide on reoxygenation-induced Ca2+ accumulation in rat cardiomyocytes

Reactive oxygen species (ROS) contribute to cell damage during reperfusion of the heart. ROS may exert their effects partly by interfering with Ca2+ homeostasis of the myocardium. The purpose of this study was to investigate the effects of hydrogen peroxide (H2O2) on Ca2+ accumulation during reoxygenation of isolated adult rat cardiomyocytes exposed to 1 h of hypoxia and to relate the effects to possible changes in release of lactate dehydrogenase (LDH), free intracellular Ca2+ ([Ca2+](i)) and Mg2+([Mg2+](i)), and mitochondrial membrane potential (Deltapsim). Cell Ca2+ was determined by 45 Ca2+ uptake. Free [Mg2+](i) and [Ca2+](i) and Deltapsim were measured by flow cytometry. Reoxygenation-induced Ca2+ accumulation was attenuated by 23 and 34% by 10 and 25 muM H2O2, respectively, added at reoxygenation. H2O2 at 100 and 250 muM increased cell Ca2+ by 50 and 83%, respectively, whereas 500 muM H2O2 decreased cell Ca2+ by 20%. H2O2 at 25 muM reduced LDH release and [Mg2+](i) and increased Deltapsim, indicating cell protection, whereas 250 muM H2O2 increased LDH release and [Mg2+](i) and decreased Deltapsim, indicating cell damage. Clonazeparn (100 muM) attenuated the increase in Ca2+ accumulation, the elevation of [Ca2+](i), and the decrease in Deltapsim induced by 100 and 250 muM H2O2 during reoxygenation. We report for the first time that 25 muM H2O2 attenuates Ca2+ accumulation, LDH release, and dissipation of Deltapsim during reoxygenation of hypoxic carchomyocytes, indicating cell protection. (C) 2004 Elsevier Inc. All rights reserved.