title: Characterization of Zn(2+) transport in Madin-Darby canine kidney cells.
abstract: The aim of this study was to characterize the mechanism implicated in Zn(2+) transport in MDCK cells. Trace elements such as Zn(2+), Cd(2+) or Cu(2+) induced MDCK cell depolarization at the micromolar level as demonstrated by bis-oxonol fluorescence and whole-cell patch experiments. This depolarization was inhibited by La(3+) and Gd(3+) and was not related to the activation of Na(+) or Cl(-) channels. Uptake of 65Zn was assessed under initial rate conditions. The kinetic parameters obtained at 37 degrees C were a K(m) of 18.9 microM and a V(max) of 0.48 nmol min(-1) (mg protein(-1)). Intracellular pH measurements using BCECF probe demonstrated that Zn(2+) transport induced a cytoplasmic acidification. The cytoplasmic acidification resulting from Zn(2+) uptake activated Na(+)/H(+) antiporter, which allowed for the recycling of protons. These data suggest that Zn(2+) enters MDCK cells through a proton-coupled metal-ion transporter, the characteristics of which are slightly different from those described for the metal transporter DCT1. This mechanism could be in part responsible of the metal transport evidenced in the distal parts of the renal tubule.
authors.affiliation: UMR-CNRS 6548, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Ducoudret
authors.forename: Olivier
authors.initials: O
authors.lastname: Barbier
authors.forename: Michel
authors.initials: M
authors.lastname: Tauc
authors.forename: Marianne
authors.initials: M
authors.lastname: Fuchs
authors.forename: Philippe
authors.initials: P
authors.lastname: Poujeol
mesh_terms: D000818:Animals; D002413:Cations, Divalent; D002460:Cell Line; D004285:Dogs; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011522:Protons; D012964:Sodium / Q000494:pharmacology; D013858:Thiobarbiturates; D015032:Zinc / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D005456:Fluorescent Dyes; D011522:Protons; D013858:Thiobarbiturates; C025284:bis(1,3-diethylthiobarbiturate)trimethineoxonol; D012964:Sodium; D015032:Zinc