Deoxyribonucleoside Triphosphates in Human Cells: Changes in Disease and Following Exposure to Drugs

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Abstract
Deoxyribonucleic acid synthesis requires adequate cellular concentrations of the four deoxyribonucleoside triphosphates. Using a sensitive enzymic assay, we have measured the concentrations (pools) of these compounds in human bone marrow cells and in lymphocytes. The mean concentrations (pmol/106 cells) in normal human bone marrow cells were: deoxyadenosine triphosphate (dATP) 1.5; deoxyguanosine triphosphate (dGTP) 0.4; thymidine triphosphate (dTTP) 1.4 and deoxycytidine triphosphate (dCTP) 0.6; and in normal phytohaemagglutinin (PHA)‐stimulated lymphocytes (72 h cultures); dATP 3.7; dGTP 1.9; dTTP 9.4 and dCTP 2.9. The deoxyribonucleoside triphosphate concentrations were increased approximately threefold in the nucleated marrow cells from patients with leukaemia and myeloproliferative diseases. PHA‐stimulation of lymphocytes caused a marked increase of the deoxyribonucleoside triphosphate concentrations, particularly of dTTP, between 24 and 48 h of culture. In PHA‐stimulated lymphocytes, the antifolate drugs methotrexate, pyrimethamine and trimethoprim, all produced a fall in dTTP and a rise in dATP concentrations within 1 h. These effects could be reversed by folinic acid. 5‐Fluorouracil caused a fall in dTTP and in dCTP but no consistent changes in dATP; hydroxyurea caused a fall in dATP with a rise in dTTP. BCNU caused a significant fall in dATP and dCTP. Dibutyryl cyclic 3′, 5′ adenosine monophosphate and theophylline had no consistent effect on the deoxyribonucleoside triphosphate concentrations. 6‐Mercaptopurine caused a fall in dATP and dGTP, the fall in dATP being marked after 4 h incubation.It is concluded that measurement of the deoxyribonucleoside triphosphates in human cells provides a new method of studying DNA synthesis in human disease states and of analysing the action of antimetabolite drugs on normal and diseased cells.