title: Sodium-dependent, concentrative nucleoside transport in Walker 256 rat carcinosarcoma cells.
abstract: Nucleoside transport in Walker 256 cells was reexamined using formycin B, a nonmetabolized analog of inosine. In the presence of dipyridamole to inhibit the equilibrative (facilitated diffusion) transporter previously described in these cells, the initial rate of uptake of 1 microM formycin B was 10-fold greater in Na(+)-containing medium than in Na(+)-free medium. In the presence of Na+ and dipyridamole the intracellular concentration of formycin B exceeded that in the medium within one min and was 6-fold greater than that of the medium by 5 min. Na(+)-dependent transport of formycin B was inhibited by low concentrations of inosine, but not thymidine. Furthermore, Na(+)-dependent transport of uridine, but not thymidine, was apparent in the presence of dipyridamole. These data indicate that Walker 256 cells have, in addition to the previously described equilibrative transporter, a concentrative nucleoside transporter. The specificity of this transporter appears to correspond to one of the two Na(+)-dependent transporters previously described in mouse intestinal epithelial cells.
authors.affiliation: Department of Biochemical and Clinical Pharmacology, St. Jude Children's Research Hospital, Memphis, TN 38101.
authors.forename: C R
authors.initials: CR
authors.lastname: Crawford
authors.forename: J A
authors.initials: JA
authors.lastname: Belt
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002279:Carcinoma 256, Walker / Q000378:metabolism*; D004176:Dipyridamole / Q000494:pharmacology; D005573:Formycins / Q000378:metabolism*; D007288:Inosine / Q000378:metabolism; D007700:Kinetics; D009705:Nucleosides / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000494:pharmacology*; D013936:Thymidine / Q000378:metabolism; D014529:Uridine / Q000378:metabolism
chemical_list: D005573:Formycins; D009705:Nucleosides; C034561:formycin B; D007288:Inosine; D004176:Dipyridamole; D012964:Sodium; D013936:Thymidine; D014529:Uridine