Early Changes in Energy Metabolism in the Myocardium Following Acute Coronary Artery Occlusion in Anesthetized Dogs

Abstract

The tissue content of energy-rich phosphates and glycolytic metabolites and the activity of myocardial enzymes were examined in the dog after producing myocardial infarction by ligating branches of the anterior descending and circumflex coronary arteries. The pattern of systolic fiber movement shown by a strain-gauge assembly differentiated ischemic from nonischemic portions of myocardium. In ischemic muscle, 30 minutes after onset of ischemia, creatine phosphate content fell from 8.0 to 1.4 µmoles/g, ATP content fell from 5.8 to 1.5 µmoles/g, lactate content rose tenfold, and α-glycerophosphate content rose fivefold. The content of energy-rich phosphates and glycolytic metabolites did not change much in nonischemic muscle. The activities of myocardial enzymes were assayed in extracts of tissue samples from ischemic and nonischemic muscle 5 to 120 minutes after coronary artery occlusion. The activities of aldolase, lactic dehydrogenase (LDH), glyceraldehydephosphate dehydrogenase, α-glycerophosphate dehydrogenase, malate dehydrogenase (MDH), and 6-phosphogluconate dehydrogenase did not change significantly in ischemic muscle during 2 hours of observation. In nonischemic muscle, phosphofructokinase activity increased 75% 5 minutes after coronary occlusion, followed by an increase in activity of isocitrate dehydrogenase, creatinephosphokinase, MDH, and LDH. The enzymatic changes in nonischemic muscle suggest metabolic changes in nonischemic muscle accompanying compensatory hyperfunction and increased energy requirements of surviving muscle.