| Both carbohydrates and fatty acids may undergo oxidation in reperfused myocardium, but substrate preference is controversial. Isolated rat hearts were perfused with lactate, acetate, and glucose, rendered ischemic for 25 minutes, and then reperfused with 0.25mM (1,2-{dollar}sp{lcub}13{rcub}{dollar}C) acetate, 1 mM (3-{dollar}sp{lcub}13{rcub}{dollar}C) lactate, and 10 mM unlabeled glucose. Hearts were freeze-clamped and extracted after 30 minutes or 45 minutes of reperfusion. {dollar}sp{lcub}13{rcub}{dollar}C NMR isotopomer analysis determined contribution of substrates to acetyl-CoA. Controls were identically treated but were not made ischemic. The relative contribution of lactate to acetyl-CoA declined in reperfused hearts, acetate preference was increased, and anaplerotic reactions were strongly stimulated relative to Tri-Carboxylic Acid (TCA) flux. Results suggest ischemia decreases lactate and increases acetate contributions to acetyl-CoA and increases anaplerotic flux during reperfusion of the myocardium. Additional studies were performed with 5 mM Aspartate and 5 mM Glutamate present under identical conditions. These amino acids did not alter functional recovery nor affect carbon entry into the TCA cycle. |
