Expression of a renal type I sodium/phosphate transporter (NaPi-1) induces a conductance in Xenopus oocytes permeable for organic and inorganic anions.

• DOI: 10.1073/pnas.93.11.5347
• Publication Date: 2002-07-26T14:36:44Z
• Authors: A E Busch; A Schuster; S Waldegger; C A Wagner; G Zempel; S Broer; J Biber; H Murer; F Lang
• Keywords: Niflumic acid; Organic anion; Probenecid

Two distinct molecular types (I and II) of renal proximal tubular brush border Na+/Pi cotransporters have been identified by expression cloning on the basis their capacity to induce Na+-dependent Pi influx in tracer experiments. Whereas type II transporters (e.g., NaPi-2 NaPi-3) resemble well known characteristics cotransport, little is about properties I transporter (NaPi-1). In contrast II, produced electrogenic transport only at high extracellular concentrations (> or =3 mM). On other hand, NaPi-1 induced a Cl- conductance Xenopus laevis oocytes, which was inhibited channel blockers [5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) > niflumic >> 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid]. Further, organic anions phenol red, benzylpenicillin (penicillin G), probenecid. These outwardly directed currents absence Cl-. studies, we observed uptake with Km 0.22 mM; NPPB acid. findings suggest that cotransporter functions also as novel anion permeable not for but anions. Such an apical could serve important role excretion anionic xenobiotics.