Impairment of mitochondrial function following reperfusion of acutely ischemic myocardium

This study examines indices of respiratory function in mitochondria prepared from transiently ischemic myocardium that had been reperfused in order to evaluate the validity of performing early surgical revascularization procedures. Experiments were performed in pigs with temporary ligation (15-80 min) of an anterior descending coronary artery followed by a 2-hr reperfusion period. Mitochondria preparations were studied simultaneously from normal and reperfused mitochondria in malate and glutamate substrates using the polarographic method. Results revealed a marked decrease of oxygen consumption of mitochondria from reperfused myocardium with relative preservation of oxidative phosphorylation (near normal ADP/O ratio). These results are compatible with a block in electron transport, a theory which was further supported by the data obtained using dinitrophenol as an uncoupler. Additional studies suggested the block was located at site I in the electron transport chain since mitochondrial oxygen consumption, including ATP-linked oxygen consumption, was enhanced by the use of succinate in combination with glutamate. The abnormal mitochondrial function observed is probably due to ischemia persisting despite reperfusion.