Influence of simulated ischemia on apoptosis Induction by oxidative stressin adult cardiomyocytes of rats

Oxidative stress may cause apoptosis of cardiomyocytes in ischemic-reperfus ed myocardium. We investigated whether ischemia-reperfusion modifies the su sceptibility of cardiomyocyte induction of apoptosis by oxidative stress. I schemia was simulated by incubating isolated cardiomyocytes from adult rats in an anoxic, glucose-free medium, pH 6.4, for 3 h. Annexin V-fluorescein isothiocyanate/propidium iodide staining and the detection of DNA laddering were used as apoptotic markers. H2O2 (7.5 mu mol/l) induced apoptosis in 2 0.1 +/- 1.8% of cells under normoxic conditions but only 14.4 +/- 1.6% (n = 6, P < 0.05) after ischemia-reoxygenation. This partial protection of isch emic-reoxygenated cells was observed despite a reduction in their cellular glutathione content, from 11.4 +/- 1.9 in normoxic controls to 2.9 +/- 0.8 nmol/mg protein (n = 3, P < 0.05). Elevation of end-ischemic glutathione co ntents by pretreatment with 1 mmol/l N-acetylcysteine entirely protected is chemic-reoxygenated cells against induction of apoptosis by H2O2. In conclu sion, ischemia-reperfusion can protect cardiomyocytes against induction of apoptosis by exogenous oxidative stress. This endogenous protective effect is most clearly demonstrated when control and postischemic cardiomyocytes a re compared at similar glutathione levels.