31P-NMR studies of glucose and glutamine metabolism in cultured mammalian cells.

31P-NMR measurements of the concentrations of phosphorus-containing metabolites in mammalian cells immobilised and perifused with glucose and glutamine as sole carbon source have shown that the intracellular Pi concentration is significantly higher in cells perifused with glutamine than with glucose. The data are consistent with the proposal that the rate of glutamine utilisation may be controlled by the activity of phosphate-activated glutaminase.