Inhibition of carbohydrate oxidation during the first minute of reperfusion after brief ischemia: NMR detection of hyperpolarized 13CO2 and H13CO

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Abstract
Isolated rat hearts were studied by 31P NMR and 13C NMR. Hyperpolarized [1‐13C]pyruvate was supplied to control normoxic hearts and production of [1‐13C]lactate, [1‐13C]alanine, 13CO2 and H13CO was 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, [1‐13C]alanine and [1‐13C]lactate appeared rapidly, demonstrating metabolism of pyruvate through two enzymes largely confined to the cytosol, alanine aminotransferase, and lactate dehydrogenase. 13CO2 and H13CO were not detected. Late after ischemia and reperfusion, the products of pyruvate dehydrogenase, 13CO2 and H13CO were 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.