Resistance of endothelial cells to anoxia-reoxygenation in isolated guinea pig hearts

The release of cytosolic enzymes from myocardial and endothelial cells in the anoxic-reoxygenated guinea pig heart was investigated. Isolated hearts were perfused with Tyrode solution in the Langendorff mode. Sixty-minute anoxic perfusion with or without glucose (5 mM) was followed by 15-min normoxic perfusion with glucose. The losses of purine-nucleoside phosphorylase (PNP) from endothelial cells and of lactate dehydrogenase (LDH) and creatine kinase (CK) from the mass of myocardial cells were determined. After 30-min anoxia, the release of LDH and CK but not of PNP increased. Reoxygenation after 60-min anoxia with glucose caused a partial recovery of tissue ATP but also an increase in leakage of LDH (11% of total in 15 min) and CK (10%) and a sudden rise in coronary resistance, indicating contracture development ("oxygen paradox"). PNP release remained low (0.5%). In hearts subjected to glucose-free anoxia, ATP levels did not rise during 15-min reoxygenation, contracture development was delayed, and the release of LDH and CK was diminished (3.1 and 2.7%, respectively). Leakage of PNP was again low (0.5%). The results indicate that cardiomyocytes are more severely injured by anoxia-reoxygenation than the coronary endothelium. The rapidly developing reoxygenation-induced injury of cardiomyocytes seems to be an energy-dependent phenomenon, since it was attenuated in hearts deprived of substrate in anoxia.