Glutathione, but not glutamine, is detected in 13C‐NMR spectra of perchloric acid extracts from C6 glioma cells

Glutamine, which is expected to be produced by C6 glioma cells, is not detected in both amino‐acid analyses and 13C‐NMR spectra of perchloric acid extracts of cells incubated for 4 h with [1‐13C]glucose in the absence of extracellular glutamine. However, the resonances of a glutamate‐linked product are observed in these spectra. The analysis of the pH dependence of chemical shifts from various glutamate‐derived compounds shows that the observed resonances came from glutathione. Glutamine and glutathione signals are in close proximity on the frequency scale, leading to possible misinterpretation of the spectra.