Uridine, but not cytidine can sustain growth of Ehrlich ascites tumor cells in glucose-deprived medium with altered proliferation kinetics.

Cell cycle kinetics and energy metabolism of Ehrlich ascites tumor cells grown in glucose-deprived medium supplemented with uridine, were investigated in order to extend our knowledge about the significance of the metabolic conversion of glucose for cell cycle progression of these cells. Viability (dye exclusion test) of uridine supplemented cells was not affected, although growth was reduced to 50 to 60% of the controls. Uridine did not significantly impair growth of controls in standard medium up to 20 mM. Studies on cell cycle progression using flow cytometry (BrdU-H33258 technique) revealed an accumulation of cells in G2M phase, which can be explained by a delay in the passage of G2M-compartment of about 12 +/- 2 h. After a 24 h culture period, 60% of the cell populations were found in G2M (30% in control cultures). This fraction increased to about 70% in the following passage. Protein and DNA synthesis corresponded to the proliferation rate. Oxygen uptake was increased by about 50%, glutamine consumption by 30%, lactate production was reduced to below 10% of the controls. The ATP/ADP concentration ratio was found in a physiological range of 4 to 6. It was calculated that cells grown in standard medium produced 60% of ATP via oxidative pathways and 40% via glycolysis; however, in glucose-free, uridine-supplemented medium the values are more than 90% and less than 10%. No significant differences in total ATP production were observed. Growth of the cells in glucose-deprived medium could not be sustained by cytidine. All our data substantiate the present concept that glycolytic ATP-production is not essential for maintenance of viability and growth of these cells.