PHYSIOLOGICAL CONCENTRATIONS OF PURINES AND PYRIMIDINES

The concentrations of bases, nucleosides, and nucleosides mono-, di- a nd tri-phosphate are compared for about 600 published values. The data are predominantly from mammalian cells and fluids. For the most impor tant ribonucleotides, average concentrations +/- SD (mu M) are: ATP, 3 ,152 +/- 1,698; GTP, 468 +/- 224; UTP, 567 +/- 460 and CTP, 278 +/- 24 2. For deoxynucleosides-triphosphate (dNTP), the concentrations in div iding cells are: dATP, 24 +/- 22; dGTP, 5.2 +/- 4.5; dCTP, 29 +/- 19 a nd dTTP 37 +/- 30. By comparison, dUTP is usually about 0.2 mu M. For the 4 dNTPs, tumor cells have concentrations of 6-11 fold over normal cells, and for the 4 NTPs, tumor cells also have concentrations 1.2-5 fold over the normal cells. By comparison, the concentrations of NTPs are significantly lower in various types of blood cells. The average c oncentration of bases and nucleosides in plasma and other extracellula r fluids is generally in the range of 0.4-6 mu M; these values are usu ally lower than corresponding intracellular concentrations. For phosph ate compounds, average cellular concentrations are: P-i, 4400; ribose- 1-P, 55; ribose-5-P, 70 and P-ribose-PP, 9.0. The metal ion magnesium, important for coordinating phosphates in nucleotides, has values (mM) of: free Mg2+, 1.1; complexed-Mg, 8.0. Consideration of experiments o n the intracellular compartmentation of nucleotides shows support for this process between the cytoplasm and mitochondria, but not between t he cytoplasm and the nucleus.