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Purpose: Mitochondrial membrane potential ([mP]) and intracellular calcium concentration ([Ca2+]i) play an important role in the mechanism of apoptosis induced by oxidative stress, however, it is unknown the relationship between [mP] and [Ca2+]i upon oxidative stress and their modification by medication. Methods: Isolated neonatal cardiomyocytes were exposed to H2O2 for 16hours and apoptotic nuclei were detected by TUNEL method. Laser confocal microscopy was used to evaluate the time lapse-changes of [Ca2+]i and [mP] in cardiomyocytes loaded with fluo-3AM and TMRE. Results: The percentage of apoptotic cells was 24 ± 5%, 37 ± 8% and 44 ± 9% induced with 50, 100 and 200μmol/L H2O2 and carvedilol (10μmol/L) decreased the apoptotic cells to 17 ± 4%, 27 ± 5% and 32 ± 5% (p < 0.05 v.s. no carvedilol group) in each concentration of H2O2, respectively. The increase of [Ca2+]i preceded the change of [mP] (time to the onset: 21.4 ± 4.6 minutes for [Ca2+]i v.s. 38 ± 5.6 minutes for [mP], p < 0.01) after the addition of H2O2. Carvedilol delayed the onset of [mP] loss (1μmol/L group 46.0 ± 3.0 minutes, 5μmol/L group 57.0 ± 6.7 minutes, 10μmol/L group 86.5 ± 9.7 minutes, p < 0.05) and also delayed the onset of [Ca2+]i increase (5μmol/L group 27.2 ± 6.3, 10μmol/L group 45.4 ± 7.7 min, p < 0.05) respectively. Conclusion: Upon oxidative stress-induced apoptosis, the increase of [Ca2+]i preceded the depolarization of [mP] and carvedilol delayed [Ca2+]i overload and inhibited the collapse of [mP], which may contribute to the inhibition of apoptosis. |
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