Enhancement by purine nucleosides and nucleotides of serum‐induced DNA synthesis in quiescent 3T3 cells

Abstract

Purine nucleotides and nucleosides were found to enhance the DNA synthesis in quiescent 3T3 cells induced either by fresh medium containing calf serum or by the addition of the β‐globulin serum fraction to depleted medium. A two to threefold enhancement has been obtained under these conditions. The adenine and hypoxanthine based compounds were more effective than the guanine ones in the concentration range tested (10⁻⁵−−10⁻³ M), while the pyrimidine compounds were without effect. The degree of enhancement obtained with the purine compounds depended on the type and amount of serum used to stimulate DNA synthesis. A maximal degree of enhancement was obtained when the purine compounds were present for only the first three hours after the addition of serum and thus 18–20 hours before the actual onset of DNA synthesis.