Biochemical alterations during unperturbed suspension growth of L1210 cells

The following parameters were evaluated at several points throughout unperturbed suspension culture growth of L1210 cells: cell volume; DNA histograms; the mean content of cellular DNA, RNA, and protein; ribonucleoside and deoxyribonucleoside triphosphate pools; phosphoribosyl pyrophosphate; and the incorporation of glycine into purine bases. The cell volume, the incorporation of glycine into purine bases, and the intracellular pools of phosphoribosyl pyrophosphate and dexoyribunucleotides began to decrease significantly during the midportion of logarithmic cell growth. However, there was no significant change in the DNA content per cell during culture growth. The RNA, protein content, and ribonucleotides all demonstrated a biphasic pattern with the highest values obtained during the midportion of logarithmic growth followed by rapid decline as the culture approached plateau growth. These intracellular fluctuations in de novo synthesis and precursor pools were correlated with the variable intracellular accumulation of three fluoropyrimidines (5-fluorouracil, 5-fluorouridine, and 5-fluorodeoxyuridine) and their active metabolites (5-fluorouridine triphosphate and 5-fluorodeoxyuridylate). These studies were performed to demonstrate that multiple biochemical alterations occur during logarithmically growing suspension cell cultures and could result in misleading conclusions of experiments with antimetabolites unless these factors are considered in the context of the performed studies.