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This Article Full Text Full Text (PDF) All Versions of this Article: 296/4/F691    most recent 90623.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Villa-Bellosta, R. Articles by Forster, I. C. Search for Related Content PubMed PubMed Citation Articles by Villa-Bellosta, R. Articles by Forster, I. C.

The Na⁺-P_i cotransporter PiT-2 (SLC20A2) is expressed in the apical membrane of rat renal proximal tubules and regulated by dietary P_i

¹Laboratory of Molecular Toxicology, University of Zaragoza, Spain; ²Institute of Physiology and Center for Integrative Human Physiology, University of Zurich, Switzerland; and ³Department of Medicine, University of Colorado Health Sciences Center, Aurora, Colorado

Submitted 19 October 2008 ; accepted in final form 8 December 2008

The principal mediators of renal phosphate (P_i) reabsorption are the SLC34 family proteins NaPi-IIa and NaPi-IIc, localized to the proximal tubule (PT) apical membrane. Their abundance is regulated by circulatory factors and dietary P_i. Although their physiological importance has been confirmed in knockout animal studies, significant P_i reabsorptive capacity remains, which suggests the involvement of other secondary-active P_i transporters along the nephron. Here we show that a member of the SLC20 gene family (PiT-2) is localized to the brush-border membrane (BBM) of the PT epithelia and that its abundance, confirmed by Western blot and immunohistochemistry of rat kidney slices, is regulated by dietary P_i. In rats treated chronically on a high-P_i (1.2%) diet, there was a marked decrease in the apparent abundance of PiT-2 protein in kidney slices compared with those from rats kept on a chronic low-P_i (0.1%) diet. In Western blots of BBM from rats that were switched from a chronic low- to high-P_i diet, NaPi-IIa showed rapid downregulation after 2 h; PiT-2 was also significantly downregulated at 24 h and NaPi-IIc after 48 h. For the converse dietary regime, NaPi-IIa showed adaptation within 8 h, whereas PiT-2 and NaPi-IIc showed a slower adaptive trend. Our findings suggest that PiT-2, until now considered as a ubiquitously expressed P_i housekeeping transporter, is a novel mediator of P_i reabsorption in the PT under conditions of acute P_i deprivation, but with a different adaptive time course from NaPi-IIa and NaPi-IIc.

brush-border membrane; inorganic phosphate; sodium-dependent transport

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