Oxygen consumption and tissue Ca2+ uptake during reoxygenation after hypoxia in the rabbit

The relationship between tissue Ca uptake and myocardial oxygen consumption during reoxygenation after 20, 40, and 60 min hypoxia was studied in the isolated arterially perfused rabbit septum. During reoxygenation after 40 and 60 min of hypoxia, tissue 47Ca2+ uptake increased significantly, and myocardial oxygen consumption (MVO2) (approximately 125% of control) was significantly greater than the prehypoxic value. Recovery of myocardial ATP content and mechanical function after 40 and 60 min of hypoxia was minimal, and it was inversely related to net increases in tissue Ca2+ uptake. In muscles perfused with Tris buffer, tissue Ca2+ gain during reoxygenation was significantly less and recovery of tissue ATP was significantly greater than in muscles perfused with Krebs-Henseleit buffer. MVO2 was not enhanced during reoxygenation after 40 min of hypoxia in muscles perfused with Tris buffer. These data suggest that tissue Ca2+ gain during reoxygenation utilizes energy from mitochondrial electron transport or from ATP hydrolysis causing increased MVO2 and depression in total adenine nucleotides and mechanical function.