Protection of reoxygenated cardiomyocytes against sarcolemmal fragility:: the role of glutathione

This study addressed the question of whether the sarcolemmal fragility of cardiomyocytes after anoxia and subsequent reoxygenation can be altered by modulation of the cellular glutathione state. Isolated ventricular cardiomyocytes (from adult rats) were exposed to 120 min anoxia and subsequently to 30 min reoxygenation. Osmotic stress was generated by reduction of medium osmolarity from 270 to 80 mosmol/l and sarcolemmal fragility assessed by the leakage of lactate dehydrogenase (LDH). Under normoxic conditions 6.7+/-1.0 % of total LDH activity was found extracellularly. Hyposmolar reoxygenation, but not hypoosmolar anoxia, increased LDH release (17.9+/-2.7% of total, P<0.05). Increasing cellular glutathione content by pretreatment with N-acetylcysteine (1 mM) reduced LDH release following hyposmolar reoxygenation (12.3+/-1.9% vs. 18.2+/-2.9% of LDH in medium, P<0.05). Depletion of glutathione content by pretreatment with buthionine sulphoximine (BSO, 200 mu M), increased LDH release following osmotic stress already in normoxia (10.5+/-1.8% of LDH in medium; P<0.05 vs. no BSO), and even further after reoxygenation (21.8+/-3.2%, P<0.05 vs. normoxia). We conclude that the increased sarcolemmal fragility in reoxygenated cardiomyocytes is due to reoxygenation in the presence of reduced antioxidant defence.