Hypoxanthine enters human vascular endothelial cells (ECV 304) via the nitrobenzylthioinosine-insensitive equilibrative nucleoside transporter
Keywords: kinetics, proteins, inhibition, endothelium, membrane, transport, ion, cell, choline, line, humans, human, lithium, sodium, carrier, adenosine, dipyridamole, article, vein, guanine, thymine, umbilical, nucleoside, rubidium, adenine, controlled, vascular, study, priority, journal, competitive, biological, dilazep, hypoxanthine, meglumine, nitrobenzylthioinosine, Endothelium,, Hypoxanthines, Thioinosine
The transport properties of the nucleobase hypoxanthine were examined in the human umbilical vein endothelial cell line ECV 304. Initial rates of hypoxanthine influx were independent of extracellular cations: replacement of Na+ with Li+, Rb+, N-methyl-D-glucamine or choline had no significant effect on hypoxanthine uptake by ECV 304 cells. Kinetic analysis demonstrated the presence of a single saturable system for the transport of hypoxanthine in ECV 304 cells with an apparent K(m) of 320 ± 10 ?M and a V(max) of 5.6 ± 0.9 pmol/106 cells per s. Hypoxanthine uptake was inhibited by the nucleosides adenosine, uridine and thymidine (apparent K(i) 41 ± 6, 240 ± 27 and 59 ± 8 ?M respectively) and the nucleoside transport inhibitors nitrobenzylthioinosine (NBMPR), dilazep and dipyridamole (apparent K(i) 2.5 ± 0.3, 11 ± 3 and 0.16 ± 0.006 ?M respectively), whereas the nucleobases adenine, guanine and thymine had little effect (50% inhibition at > 1 mM). ECV 304 cells were also shown to transport adenosine via both the NBMPR-sensitive and -insensitive nucleoside carriers. Hypoxanthine specifically inhibited adenosine transport via the NBMPR-insensitive system in a competitive manner (apparent K(i) 290 ± 14 ?M). These results indicate that hypoxanthine entry into ECV 304 endothelial cells is mediated by the NBMPR-insensitive nucleoside carrier present in these cells.
|Título de la Revista:||BIOCHEMICAL JOURNAL|
|Editorial:||Portland Press, Ltd.|
|Fecha de publicación:||1996|
|Página de inicio:||843|