This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dahlig-Harley, E. Articles by Cass, C. E. Search for Related Content PubMed PubMed Citation Articles by Dahlig-Harley, E. Articles by Cass, C. E.

Transport of Uridine and 3-Deazauridine in Cultured Human Lymphoblastoid Cells¹

Cancer Research Group (McEachern Laboratory) [E. D-H., A. R. P. P., C. E. C.], Department of Biochemistry [A. R. P. P., C. E. C.], and Department of Chemistry [M. J. R.], University of Alberta, Edmonton, Alberta, Canada T6G 2H7

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: K_m, 0.23 ± 0.02 and 0.25 ± 0.07 mM; and V_max, 35 ± 2 and 57 ± 10 pmol/µl 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 (pK_a, 6.5), were: K_m, 0.52 ± 0.01 and 0.51 ± 0.03 mM; and V_max, 28 ± 0.5 and 24 ± 0.9 pmol/µl 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.

¹ Supported by the Medical Research Council of Canada and the National Cancer Institute of Canada.

² To whom requests for reprints should be addressed.

Received 5/23/83. Accepted 10/ 4/83.