title: Multiple sodium-dependent nucleoside transport systems in bovine renal brush-border membrane vesicles.
abstract: Na(+)-dependent nucleoside transport was examined in bovine renal brush-border membrane vesicles. Two separate Na+/nucleoside cotransporters were shown to be present: (1) a system specific for purine nucleosides and uridine, designated as the N1 carrier, and (2) an Na(+)-dependent nucleoside transporter that accepts pyrimidine nucleosides, adenosine and analogues of adenosine, designated as the N2 system. Both systems exhibit a high affinity for nucleosides (apparent Km values approximately 10 microM), are insensitive to inhibition by facilitated-diffusion nucleoside transport inhibitors, are rheogenic and exhibit a high specificity for Na+. Na+ increases the affinity of the influx of guanosine and thymidine, nucleosides that serve as model permeants for the N1 and N2 nucleoside transporters respectively. The Na+/nucleoside coupling stoichiometry is consistent with 1:1 for both carriers.
authors.affiliation: Biological Laboratory, University of Kent, Canterbury, U.K.
authors.forename: T C
authors.initials: TC
authors.lastname: Williams
authors.forename: S M
authors.initials: SM
authors.lastname: Jarvis
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D005947:Glucose / Q000494:pharmacology; D006151:Guanosine / Q000378:metabolism; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D033703:Nucleoside Transport Proteins; D009705:Nucleosides / Q000378:metabolism* / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*; D013936:Thymidine / Q000378:metabolism; D014316:Tritium; D014529:Uridine / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; D033703:Nucleoside Transport Proteins; D009705:Nucleosides; D014316:Tritium; D006151:Guanosine; D012964:Sodium; D005947:Glucose; D013936:Thymidine; D014529:Uridine