title: Expression of rat ileal Na(+)-sulphate cotransport in Xenopus laevis oocytes: functional characterization.
abstract: Small-intestinal sulphate absorption is a Na(+)-dependent process having its highest rate in the ileum; it involves brush-border membrane Na(+)-sulphate cotransport. Injection of rat ileal mRNA into Xenopus laevis oocytes induced Na(+)-dependent sulphate uptake in a dose-dependent manner, with no apparent effect on Na(+)-independent sulphate uptake. For mRNA-induced transport, the apparent Km value for sulphate interaction was 0.6 +/- 0.2 mM and that for sodium interaction was 25 +/- 2 mM (Hill coefficient: 2.3 +/- 0.3). mRNA-induced transport, was inhibited by thiosulphate, but not by phosphate or 4,4,'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS). Using a rat renal Na(+)-sulphate cotransporter cDNA as a probe [NaSi-1; Markovich et al. (1993) Proc Natl Acad Sci USA 90:8073-8077], the highest hybridization signals (2.3 kb and 2.9 kb) were obtained in size fractions showing the highest expression of Na(+)-dependent sulphate transport in oocytes. Hybrid depletion experiments using antisense oligonucleotides (from the NaSi-1 cDNA sequence), provided further evidence that rat small-intestinal (ileal) Na(+)-sulphate cotransport is closely related to rat proximal-tubular brush-border membrane Na(+)-sulphate cotransport.
authors.affiliation: Institute of Physiology, University of Zürich, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Perego
authors.forename: D
authors.initials: D
authors.lastname: Markovich
authors.forename: F
authors.initials: F
authors.lastname: Norbis
authors.forename: T
authors.initials: T
authors.lastname: Verri
authors.forename: V
authors.initials: V
authors.lastname: Sorribas
authors.forename: H
authors.initials: H
authors.lastname: Murer
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins; D018076:DNA, Complementary; D007082:Ileum / Q000378:metabolism*; D066298:In Vitro Techniques; D017136:Ion Transport / Q000502:physiology; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D000077003:Sodium Sulfate Cotransporter; D013431:Sulfates / Q000378:metabolism*; D027981:Symporters; D014982:Xenopus laevis
chemical_list: D002352:Carrier Proteins; D027682:Cation Transport Proteins; D018076:DNA, Complementary; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D000077003:Sodium Sulfate Cotransporter; D013431:Sulfates; D027981:Symporters; D012964:Sodium