NMR indirect detection of glutamate to measure citric acid cycle flux in the isolated perfused mouse heart

C-13-edited proton nuclear magnetic resonance (NMR) spectroscopy was used to follow enrichment of glutamate C3 and C4 with a temporal resolution of similar to 20 s in mouse hearts perfused with C-13-enriched substrates. A fit of the NMR data to a kinetic model of the tricarboxylic acid (TCA) cycle and related exchange reactions yielded TCA cycle and exchange fluxes between a-ketoglutarate and glutamate. These fluxes were substrate-dependent and decreased in the order acetate ( V-tea=14.1 mu mol g(-1) min(-1); V-x=26.5 mu mol g(-1) min(-1)) > octanoate (V-tea= 6.0 mu mol g(-1) min(-1); V-x = 16.1 mu mol g(-1) min(-1)) > lactate (V-tea = 4.2 mu mol g(-1) min(-1); V-x = 6.3 mu mol g(-)1 min(-1)). (C) 2001 Published by Elsevier Science BN. on behalf of the Federation of European Biochemical Societies.