Kinetics of the chloride-anion exchanger of brush-border membrane vesicles isolated from chicken jejunum.
The kinetic parameters of the apical Cl(-)-anion exchanger of chicken jejunum have been evaluated using brush-border membrane vesicles. SITS inhibited pH gradient-driven Cl- uptake in a dose-dependent manner with a IC50 of 700 microM. In the presence of a pH gradient (pH 7.7 inside, 5.5 outside), Cl- uptake tends to saturate with increasing external Cl- concentration. With 5 mM SITS the relationship between 36Cl- uptake and external Cl- concentration was linear. SITS-insensitive Cl- uptake may represent a diffusion component and has an apparent diffusion constant, Kd, of 0.068 +/- 0.002 nmol/mg protein per 15 s per mM. Eadie-Hofstee analysis of the data obtained by subtracting the SITS-insensitive component from the total uptake indicates a single transport system with a Km of 5 +/- 0.9 mM. A 50 mM outwardly directed bicarbonate gradient increased the Vmax from 3.63 +/- 0.33 to 6.40 +/- 0.54 nmol/mg protein per 15 s. The initial rate of H2-DIDS-sensitive Cl- uptake increased as the intravesicular pH increased, with a Hill coefficient greater than one. An intra- to extravesicular gradient of Cl-, I- and HCO3- stimulated Cl- uptake in the absence of a pH gradient.
Departamento de Fisiología y Biología Animal, Facultad de Farmacia, Universidad de Sevilla, Spain.
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Cano
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Ilundáin
D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000737:chemistry*; D017920:Antiporters / Q000737:chemistry*; D002645:Chickens; D002712:Chlorides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007583:Jejunum / Q000737:chemistry* / Q000187:drug effects / Q000648:ultrastructure; D007700:Kinetics; D008871:Microvilli / Q000737:chemistry; D011868:Radioisotopes
D000838:Anions; D017920:Antiporters; D002712:Chlorides; D011868:Radioisotopes; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid