Furine Nucleotide Metabolism and Nucleotide Pool Sizes in Synchronized Lymphoma L5178Y Cells1

Mouse lymphoma L5178Y cells in culture were syn chronized by exposure to thymidine and Colcemid. At four times during the cell cycle, various aspects of purine metab olism 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 en zyme activities of the purine phosphoribosyltransferases, adenosine monophosphate deaminase and guanosine monophosphate reducÃ-ase,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 through out the cell cycle, whereas uridine diphosphate-glucose, cytidine triphosphate, and uridine triphosphate concentra tions appeared to decrease in the S and G2 phases.