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

13C‐edited proton nuclear magnetic resonance (NMR) spectroscopy was used to follow enrichment of glutamate C3 and C4 with a temporal resolution of ∼20 s in mouse hearts perfused with 13C‐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 (V tca) and exchange (V x) fluxes between α‐ketoglutarate and glutamate. These fluxes were substrate‐dependent and decreased in the order acetate (V tca=14.1 μmol g−1 min−1; V x=26.5 μmol g−1 min−1)>octanoate (V tca=6.0 μmol g−1 min−1; V x=16.1 μmol g−1 min−1)>lactate (V tca=4.2 μmol g−1 min−1; V x=6.3 μmol g−1 min−1).

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