Alteration in calcium metabolism in mitochondria isolated from ischemic and reperfused myocardium

This study determines the effect of ischemia and reperfusion on energy-linked Ca2+ uptake by myocardial mitochondria. The left anterior descending coronary artery was occluded in 14 mature pigs for 2 hr. In seven animals the ligature was released and the ischemic zone reperfused for 2 additional hours. After sacrifice, mitochondrial function was measured in normal and reperfused or ischemic areas of the left ventricle, using a polarographic method. Mitochondria were prepared without EDTA by standard procedures and Ca2+ uptake measured by 45Ca2+ isotope tracer. Uptake of Ca2+ by mitochondria derived from ischemic myocardium is markedly impaired with or without phosphate. Reperfusion may accentuate this impairment. The presence of exogenous Ca2+ inhibits the ability of ischemic or reperfused mitochondria to phosphorylate ADP.