Crossover plot study of glycolytic intermediates in the ischemic canine heart

Effects of regional ischemia on myocardial glycolysis were studied by measuring the levels of glycolytic intermediates in the endo- and epicardial layers of the left ventricle in dogs anesthetized with pentobarbital. Regional ischemia was induced by ligating a small branch of the left anterior descending coronary artery. The myocardial tissue samples were removed before and 1.5, 3, 7, or 30 min after coronary artery ligation. Based on a crossover plot study of the glycolytic intermediates, it is suggested that the activity of glycogen phosphorylase was accelerated, while that of phosphofructokinase was inhibited in ischemic myocardium samples removed 1.5, 3, 7, and 30 min after ligation. When the frozen myocardium was allowed to stand at room temperature for 10 min, the crossover plot study revealed acceleration of phosphofructokinase activity. The metabolic response to regional ischemia of the endocardial layers was more marked than that of the epicardial. During ischemia the levels of adenine nucleotides did not change significantly, but those of citrate and hydrogen ions increased significantly. It appears that inhibition of myocardial phosphofructokinase activity during ischemia is partly due to an increase in the levels of citrate and hydrogen ions in the ischemic tissue.