Mancuso A, Sharfstein S T, Fernandez E J, Clark D S, Blanch H W
MRI Unit, VAMC 114M, University of California, San Francisco, 4150 Clement St., San Francisco, California 94121, USA.
Biotechnol Bioeng. 1998 Jan 20;57(2):172-86.
The effect of changes in extracellular glutamine level on metabolism of a murine hybridoma was examined with in vivo nuclear magnetic resonance (NMR) spectroscopy. Cells were cultured in a hollow-fiber bioreactor at high cell density to allow intracellular metabolite levels to be determined on a metabolically relevant time scale. Steady infusions of [1-13C] glucose were used to label glycolytic and tricarboxylic acid 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 secondary metabolism. The changes in glutamine concentration had several effects on primary and secondary metabolism, depending on the rate the changes were made. For a brief reduction in feed glutamine concentration from 4 to 0 mM (which produced a rapid change from 0.67 to approximately 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 was 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 residual glutamine), much smaller changes were observed even though the concentration of glutamine at the reduced feed level was very low. Energy metabolism did not appear to be limited by glutamine at 0.08 mM, which suggests that significant futile cycling may occur in energy producing 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.
采用体内核磁共振（NMR）光谱法研究了细胞外谷氨酰胺水平变化对小鼠杂交瘤代谢的影响。细胞在中空纤维生物反应器中以高细胞密度培养，以便在与代谢相关的时间尺度上测定细胞内代谢物水平。持续输注[1-13C]葡萄糖以标记糖酵解和三羧酸循环中间体，从而在环境谷氨酰胺水平变化期间通过NMR光谱进行连续监测。还对细胞外培养基样品进行了分析，以确定谷氨酰胺对与初级和次级代谢相关的其他代谢物的影响。谷氨酰胺浓度的变化对初级和次级代谢有多种影响，这取决于变化的速率。当饲料中谷氨酰胺浓度从4 mM短暂降至0 mM（导致残余谷氨酰胺从0.67 mM迅速降至约0 mM）时，观察到通常与能量产生相关的代谢物消耗速率发生了很大变化。抗体合成受到强烈刺激，氮代谢也发生了显著改变。当谷氨酰胺浓度从2.4 mM更长期地降至1.2 mM（导致残余谷氨酰胺从0.30 mM缓慢降至0.08 mM）时，尽管降低后的饲料水平下谷氨酰胺浓度非常低，但观察到的变化要小得多。在0.08 mM时，能量代谢似乎不受谷氨酰胺的限制，这表明当有过量的葡萄糖和谷氨酰胺时，能量产生途径中可能会发生显著的无效循环。然而，这种细胞外谷氨酰胺浓度似乎影响了一些需要谷氨酰胺氨基的合成代谢途径。
