Purine Nucleotide Metabolism and Nucleotide Pool Sizes in Synchronized Lymphoma L5178Y Cells¹ Free

Mouse lymphoma L5178Y cells in culture were synchronized by exposure to thymidine and Colcemid. At four times during the cell cycle, various aspects of purine metabolism were examined with the use of radioactive purine bases. In all experiments the uptake and conversion of bases to nucleotides was rate limiting for ribonucleoside triphosphate synthesis. Cell cycle variations in the apparent enzyme activities of the purine phosphoribosyltransferases, adenosine monophosphate deaminase and guanosine monophosphate reductase, were observed. Purine and pyrimidine nucleotide pool sizes were determined by high-pressure liquid chromatography. After correction for increases in cell volume, it was observed that nicotinamide adenine dinucleotide, adenosine triphosphate, and guanosine triphosphate concentrations remained relatively constant throughout the cell cycle, whereas uridine diphosphate-glucose, cytidine triphosphate, and uridine triphosphate concentrations appeared to decrease in the S and G₂ phases.