Nucleic Acid Metabolism in Ehrlich Ascites Tumor Cells

The incorporation of P32 into DNA by washed Ehrlich ascites tumor cells in vitro was found to require oxygen and a physiological temperature, pH, and ionic strength, but could be carried out in 0.9 per cent saline without additional substrate, precursors, or cofactors. Formate-C14 was also incorporated into DNA thymine under these conditions, but the incorporation of formate-C14 into purines and of labeled adenine and orotic acid into nucleic acids was markedly reduced in comparison to cells incubated in ascitic fluid. Addition of 4-amino-5-imidazole carboxamide restored the ability of the washed cells to incorporate labeled formate into purines but did not increase the incorporation of P32 or labeled orotic acid.