3-deazauridine and Leukemia--Lymphoid

The transport of uridine and 3-deazauridine was compared in two lines of cultured human lymphoblastoid cells that differ in their sensitivity to 3-deazauridine apparently because of reduced uridine-cytidine kinase activity in the resistant line. The kinetic parameters (+/- S.E.) of uridine transport were similar in the two cell lines: Km, 0.23 +/- 0.02 and 0.25 +/- 0.07 mM; and Vmax, 35 +/- 2 and 57 +/- 10 pmol/microliter of cell water per sec, respectively, for 6410/MP (parental) and 6410/MP/DU (resistant) cells. 3-Deazauridine, while transported with similar kinetic characteristics in both cell lines, was not as good a substrate for the nucleoside transporter as was uridine, and its transport was dependent on pH. Kinetic parameters, determined using calculated concentrations of the undissociated form of 3-deazauridine (pKa, 6.5), were: Km, 0.52 +/- 0.01 and 0.51 +/- 0.03 mM; and Vmax, 28 +/- 0.5 and 24 +/- 0.9 pmol/microliter of cell water per sec, respectively, for 6410/MP and 6410/MP/DU cells. At pH 8, a condition in which 97% of 3-deazauridine molecules are ionized, rates of transport were almost zero. It is concluded that the undissociated form of 3-deazauridine is the substrate for the nucleoside transporter.

Topics: 3-Deazauridine; Biological Transport; Cell Line; Humans; Hydrogen-Ion Concentration; Kinetics; Leukemia, Lymphoid; Uridine

Topics: 3-Deazauridine; Arabinofuranosylcytosine Triphosphate; Arabinonucleotides; Cells, Cultured; Chromatography, High Pressure Liquid; Cytarabine; Cytidine Triphosphate; Humans; Leukemia; Leukemia, Lymphoid; Leukemia, Myeloid, Acute; Uracil Nucleotides; Uridine; Uridine Triphosphate

A rapid high-pressure liquid chromatographic assay for the detection and quantitation of 3-deazauridine-5'-triphosphate (deazaUTP), the active metabolite of the anticancer drug 3-deazauridine (deazaUrd), in cell extracts is described. This procedure permits the simultaneous detection and quantitation of CTP, the cellular concentration of which is affected by treatment with deazaUrd. Human lymphoblastoid cells (line CCRF-CEM) treated with 100 nmols of deazaUrd/ml in culture accumulate deazaUTP to greater than 25 nmols/10(7) cells after 4 hours. The concentration of CTP in these cells decreased exponentially with a half-life of 1.1 hours. After these cells had been incubated with 100 nmols of deazaUrd/ml and were resuspended in drug-free medium, the intracellular deazaUTP concentration decreased exponentially with a half-life of 3.4 hours. This assay has been applied to clinical studies of deazaUrd; high cellular deazaUTP concentrations have been detected in brain tumor tissue after deazaUrd infusion.

Topics: 3-Deazauridine; Brain Neoplasms; Chromatography, High Pressure Liquid; Humans; In Vitro Techniques; Leukemia, Lymphoid; Male; Middle Aged; Neoplasms; Neoplasms, Experimental; Nucleotides; Time Factors; Uridine; Uridine Triphosphate