EFFECT OF EXTRACELLULAR GLUTAMINE CONCENTRATION ON PRIMARY AND SECONDARY METABOLISM OF A MURINE HYBRIDOMA - AN IN-VIVO C-13 NUCLEAR-MAGNETIC-RESONANCE STUDY

The effect of changes in extracellular glutamine level on metabolism o f a murine hybridoma was examined with in vivo nuclear magnetic resona nce (NMR) spectroscopy, Cells were cultured in a hollow-fiber bioreact or at high cell density to allow intracellular metabolite levels to be determined an a metabolically relevant time scale. Steady infusions o f [1-C-13] glucose were used to label glycolytic and tricarboxylic aci d cycle intermediates, which permitted continuous monitoring with NMR spectroscopy during changes in environmental glutamine level, Samples of the extracellular medium were also analyzed to determine the effect of glutamine on other metabolites associated with primary and seconda ry metabolism The changes in glutamine concentration had several effec ts on primary and secondary metabolism, depending on the rare the chan ges were made. For a brief reduction in feed glutamine concentration f rom 4 to 0 mM (which produced a rapid change from 0.67 to similar to 0 mM in residual glutamine), large changes were observed in the rate of consumption of metabolites normally associated with energy production . Antibody synthesis was strongly stimulated and nitrogen metabolism w as significantly altered. For a more prolonged reduction from 2.4 to 1 .2 mM (which produced a slower reduction from 0.30 to 0.08 mM in resid ual glutamine), much smaller changes were observed even though the con centration of glutamine at the reduced feed level was very low. Energy metabolism did not appear io be limited by glutamine at 0.08 mM, whic h suggests that significant futile cycling may occur in energy produci ng pathways when excess glucose and glutamine are available, However, this concentration of extracellular glutamine appeared to affect some anabolic pathways, which require amino groups from glutamine. (C) 1998 John Wiley & Sons, Inc.