Fig. 6. Two two-dimensional [1H-13C] heteronuclear single quantum coherence spectroscopy nuclear magnetic resonance spectra are shown superimposed, one overlaid onto the other. Only of a small portion of the large two-dimensional spectrum is displayed. Contours, which represent metabolites that have a 1H group having a chemical bond to a 13C nucleus, appear at coordinates corresponding to the 13C and 1H chemical shifts of their molecular locations. Slices were taken at t = 5 h, at the end of recovery from oxidative stress. The metabolizable substrates in the case of one plot (green contours ) were 0 mm glucose together with 10 mm [3-13C]pyruvate. In this plot, which is from data acquired in our previous study, 21 metabolism of pyruvate created a distribution of 13C labels among metabolic products. In the case of the second two-dimensional plot (red contours ), the metabolizable substrates were 2 mm glucose together with 20 mm 13C-ethyl pyruvate, with the 13C label being located as in figure 1, so that [3-13C]pyruvate would be produced when ethyl pyruvate is cleaved. Metabolism of 13C-ethyl pyruvate distributed the 13C label to metabolites (red contours ) that overlapped perfectly with metabolites produced from [3-13C]pyruvate (green contours ). Cr = creatine; GABA =γ-aminobutyric acid; PCr = phosphocreatine.