title: Basolateral localization of flounder Na+-dicarboxylate cotransporter (fNaDC-3) in the kidney of Pleuronectes americanus.
abstract: The purpose of this study was to provide functional and immunocytochemical evidence for the location of the winter flounder ( Pleuronectes americanus) sodium-dicarboxylate cotransporter-3 (fNaDC-3) in the basolateral membrane of proximal tubule cells. fNaDC-3 was expressed in Xenopus laevis oocytes. Lowering the external pH from 7.5 to 6.5 or 5.5 modestly decreased the uptake of [(14)C]succinate into fNaDC-3 expressing oocytes, but markedly increased the uptake of [(14)C]citrate. As measured by the two-electrode voltage-clamp technique, the citrate concentration eliciting half-maximal current, K(0.5), decreased from 490 microM at pH 7.5 to 32 microM at pH 6.0. The maximal inwards current, Delta I(max), increased from -27 to -72 nA, when bath pH was changed from 7.5 to 6.0. These data suggest that fNaDC-3 translocates preferably divalent citrate. cis-Aconitate, a tricarboxylate that interacts exclusively with basolateral sodium-dicarboxylate cotransport in the rat kidney, was translocated by fNaDC-3 with a K(0.5) of 300 microM. Antibodies raised against an NaDC-3-specific peptide reacted with the basal cell side of flounder renal proximal tubule segment II (PII). No other structures were stained, indicating that fNaDC-3 is located exclusively in the basolateral membrane of PII cells. We assume that fNaDC-3 provides PII cells with Krebs cycle intermediates as fuels and with alpha-ketoglutarate to drive organic anion secretion.
authors.affiliation: Max-Planck Institut für molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
authors.forename: Hartmut
authors.initials: H
authors.lastname: Hentschel
authors.forename: Birgitta C
authors.initials: BC
authors.lastname: Burckhardt
authors.forename: Beate
authors.initials: B
authors.lastname: Schölermann
authors.forename: Lars
authors.initials: L
authors.lastname: Kühne
authors.forename: Gerhard
authors.initials: G
authors.lastname: Burckhardt
authors.forename: Jürgen
authors.initials: J
authors.lastname: Steffgen
mesh_terms: D000156:Aconitic Acid / Q000378:metabolism; D000818:Animals; D016764:Cell Polarity / Q000502:physiology; D019343:Citric Acid / Q000378:metabolism; D029382:Dicarboxylic Acid Transporters / Q000378:metabolism*; D029941:Fish Proteins / Q000378:metabolism*; D005432:Flounder; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D019802:Succinic Acid / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D029382:Dicarboxylic Acid Transporters; D029941:Fish Proteins; D019343:Citric Acid; D000156:Aconitic Acid; D019802:Succinic Acid