MYOCARDIAL-METABOLISM AND FUNCTION IN ACUTELY ISCHEMIC AND HYPOXEMIC ISOLATED RAT HEARTS

We tested the hypothesis that residual oxygen supply during acute low- flow ischaemia or hypoxemia is a major regulator of myocardial perform ance, metabolism and recovery. Rat hearts were exposed for 20 min to e ither ischemia (coronary now reduced to 10% of baseline), hypoxemia (o xygen content reduced to 10% baseline) or a ''mixed'' condition (combi ned ischaemia and hypoxemia). The oxygen supply (coronary now x oxygen content) was matched in all groups (n=16 per group), Hypoxemic hearts had the highest performance (systolic and developed pressures, +/-dP/ dt(max) and oxygen uptake) and content of IMP and AMP. Ischaemic heart s had the highest content of ATP, phosphocreatine, adenine nucleotides and purines, As now and/or oxygenation were restored, post-ischemic h earts showed better functional and metabolic recovery than post-hypoxe mic ones. ''Mixed'' hearts were more similar to hypoxemic ones during oxygen shortage but to ischemic ones during recovery. We conclude that as oxygenation is critically limiting, coronary now is relatively mor e important than oxygen supply in determining myocardial function, met abolism and recovery, most likely secondary to changes in the metaboli sm of diffusible substances.