Cell viability and nucleic acid metabolism after exposure of HeLa cells to excess thymidine and deoxyadenosine

Treatment of HeLa S-3 cells with excess thymidine (2 mM) caused blocking of DNA synthesis, which resulted in a synchronization of the cells after removal of thymidine. Continued synthesis of RNA and protein suggests an “unbalanced growth” syndrome with a deficiency in the deoxycytidylate moiety analogous to states induced by 1-β- d-arabinofuranosyl cytosine or 5-fluorodeoxyuridine. Exposure of cells to excess deoxyadenosine produces a loss of cell viability accompanied by an inhibition of DNA, RNA, and protein synthesis.