The effects of media concentrations of glucose andglutamine on the intracellular nucleotide pools andoxygen uptake rates of a murine antibody-secretinghybridoma cell line were investigated. Cells takenfrom mid-exponential phase of growth were incubated inmedium containing varying concentrations of glucose(0-25 mM) and glutamine (0-9 mM). The intracellularconcentrations of ATP, GTP, UTP and CTP, and theadenylate energy charge increased concomitantly withthe medium glucose concentration. The total adenylatenucleotide concentration did not change over a glucose concentration range of 1-25 mM but therelative levels of AMP, ADP and ATP changed as theenergy charge increased from 0.36 to 0.96. Themaximum oxygen uptake rate (OUR) was obtained in thepresence of 0.1-1 mM glucose. However at glucoseconcentrations >1 mM the OUR decreased suggestinga lower level of aerobic metabolism as a result of theCrabtree effect.A low concentration of glutamine (0.5 mM) caused asignificant increase (45-128%) in the ATP, GTP,CTP, UTP, UDP-GNac, and NAD pools and a doubling ofthe OUR compared to glutamine-free cultures. Theminimal concentration of glutamine also caused anincrease in the total adenylate pool indicating thatthe amino acid may stimulate thede novosynthesis of nucleotides. However, all nucleotidepools and the OUR remained unchanged within the rangeof 0.5-9 mM glutamine.Glucose was shown to be the major substrate forenergy metabolism. It was estimated that in thepresence of high concentrations of glucose (10-25 mM),glutamine provided the energy for the maintenance ofup to 28% of the intracellular ATP pool, whereas theremainder was provided by glucose metabolism.