Inhibition of carbohydrate oxidation during the first minute of reperfusion after brief ischemia: NMR detection of hyperpolarized 13 CO 2 and H 13 CO 3 −

Isolated rat hearts were studied by 31 P NMR and 13 C NMR. Hyperpolarized [1‐ 13 C]pyruvate was supplied to control normoxic hearts and production of [1‐ 13 C]lactate, [1‐ 13 C]alanine, 13 CO 2 and H 13 CO   − 3was monitored with 1‐s temporal resolution. Hearts were also subjected to 10 min of global ischemia followed by reperfusion. Developed pressure, heart rate, oxygen consumption, [ATP], [phosphocreatine], and pH recovered within 3 min after the ischemic period. During the first 90 s of reperfusion, [1‐ 13 C]alanine and [1‐ 13 C]lactate appeared rapidly, demonstrating metabolism of pyruvate through two enzymes largely confined to the cytosol, alanine aminotransferase, and lactate dehydrogenase. 13 CO 2 and H 13 CO   − 3were not detected. Late after ischemia and reperfusion, the products of pyruvate dehydrogenase, 13 CO 2 and H 13 CO   − 3were easily detected. Using this multinuclear NMR approach, we established that during the first 90 s of reperfusion PDH flux is essentially zero and recovers within 20 min in reversibly‐injured myocardium. Magn Reson Med 60:1029–1036, 2008. © 2008 Wiley‐Liss, Inc.