The effect of glucose and glutamine on the intracellular nucleotide pool and oxygen uptake rate of a murine hybridoma

The effects of media concentrations of glucose and glutamine on the intrace llular nucleotide pools and oxygen uptake rates of a murine antibody-secret ing hybridoma cell line were investigated. Cells taken from mid-exponential phase of growth were incubated in medium containing varying concentrations of glucose (0-25 mM) and glutamine (0-9 mM). The intracellular concentrati ons of ATP, GTP, UTP and CTP, and the adenylate energy charge increased con comitantly with the medium glucose concentration. The total adenylate nucle otide concentration did not change over a glucose concentration range of 1- 25 mM but the relative levels of AMP, ADP and ATP changed as the energy cha rge increased from 0.36 to 0.96. The maximum oxygen uptake rate (OUR) was o btained in the presence of 0.1-1 mM glucose. However at glucose concentrati ons > 1 mM the OUR decreased suggesting a lower level of aerobic metabolism as a result of the Crabtree effect. A low concentration of glutamine (0.5 mM) caused a significant increase (45-128%) in the ATP, GTP, CTP, UTP, UDP- GNac, and NAD pools and a doubling of the OUR compared to glutamine-free cu ltures. The minimal concentration of glutamine also caused an increase in t he total adenylate pool indicating that the amino acid may stimulate the de novo synthesis of nucleotides. However, all nucleotide pools and the OUR r emained unchanged within the range of 0.5-9 mM glutamine. Glucose was shown to be the major substrate for energy metabolism. It was estimated that in the presence of high concentrations of glucose (10-25 mM), glutamine provid ed the energy for the maintenance of up to 28% of the intracellular ATP poo l, whereas the remainder was provided by glucose metabolism.