Insight into metabolism of CHO cells at low glucose concentration on the basis of the determination of intracellular metabolites

Glucose pulse culture was employed to characterize the growth and metabolism of Chinese hamster ovary (CHO) cells at low glucose concentration. Cell growth was gradually limited when the glucose concentration decreased to below 1.22 mmol/l. Correspondingly, in comparison with the culture at above 4.8 mmol/l glucose, the intracellular concentrations of ATP decreased by 8%, 19% and 47% at the glucose concentrations of 1.2, 0. 54, and 0.25 mmol/l, respectively, showing the shortage of energy supply might result in growth limitation at low glucose concentration. The specific consumption rates of Gln, Ser, His, Thr, Arg, Tyr, Cys2, Val, Met, Phe, Ile, Leu and Lys increased at glucose concentration below 0.54 mmol/l, implying that these amino acids were mainly catabolized instead of used as “building bricks” in protein synthesis under glucose limitation. Both intracellular Asp and Glu are always accumulated under any conditions, while intracellular concentrations of other amino acids, such as Ser, Thr, Arg, Tyr, Ala, Val, Met, Phe, Ile and Leu, increased with the decrease in the glucose concentration. There was no obvious difference in the intracellular concentrations of organic acids at different glucose concentrations. Moreover, high concentrations of intracellular malate and undetectable iso-citrate were observed, implying that citrate might be intercepted from the TCA cycle for other anabolisms.