Effects of altered ribonucleotide concentrations on ribonucleotide reduction in intact Chinese hamster ovary cells

The effect of changes in ribonucleoside triphosphate concentrations on those of deoxyribonucleotides has been determined in Chinese hamster ovary K-1 cells. Ribonucleoside triphosphate concentrations were manipulated by the use of drugs or naturally occurring purines or pyrimidines. Changes in the concentration of each ribonucleoside triphosphate led to changes in the concentration of each corresponding deoxyribonucleoside triphosphate. The relationships between the concentrations of CTP and dCTP and between those of GTP and dGTP were linear over a wide range. The relationship between the concentrations of ATP and dATP was linear over the narrow range studied, while the relationship between UTP and dTTP concentrations was curvilinear. Overall, these results demonstrate that ribonucleotides play an important role in controlling deoxyribonucleotide concentrations but the exact mechanism of this control remains to be determined.