Use of a single C-13 NMR resonance of glutamate for measuring oxygen consumption in tissue

A kinetic model of the citric acid cycle for calculating oxygen consumption from C-13 nuclear magnetic resonance (NMR) multiplet data has been develop ed. Measured oxygen consumption (M(V) over dot O-2) was compared with M(V) over dot O-2, predicted by the model with C-13 NMR data obtained from rat h earts perfused with glucose and either [2-C-13]acetate or [3-C-13]pyruvate. The accuracy of M(V) over dot O-2 measured from three subsets of NMR data was compared: glutamate C-4 and C-3 resonance areas; the doublet C4D34 (exp ressed as a fraction of C-4 area); and C-4 and C-3 areas plus several multi plets of C-2, C-3, and C-4. M(V) over dot O-2 determined by set 2 (C4D34 on ly) gave the same degree of accuracy as set 3 (complete data); both were su perior to set 1 (C-4 and C-3 areas). Analysis of the latter suffers from th e correlation between citric acid cycle flux and exchange between alpha-ket oglutarate and glutamate, resulting in greater error in estimating M(V) ove r dot O-2. Analysis of C4D34 is less influenced by correlation between para meters, and this single measurement provides the best opportunity for a non invasive measurement of oxygen consumption.