Action of deoxyadenosine on nucleic acid synthesis by tumor cells in the presence of a deaminase inhibitor

: Deoxyadenosine, which was phosphorylated to dATP, inhibited DNA synthesis in malignant cells. However, on incubation of the substance in vitro with Zaidela ascites hepatoma cells the inhibitory effect was gradually decreased due to dephosphorylation of dATP and to deamination of deoxyadenosine to deoxyinosine. In order to prolong the inhibition of nucleic acids synthesis, N-6-methyl adenosine, which was recognized as an inhibitor of adenosine deaminase, was added to the cells. Optimal inhibition of DNA synthesis was observed in presence of deoxyadenosine and N-6-methyl adenosine at 1 with 10-minus 3 M concentration. Addition of N-6-methyl adenosine, after incubation with deoxyadenosine within 2 hrs, caused more prolonged inhibition of DNA and RNA synthesis than it was observed in presence of deoxyadenosine.