title: Conductive pathways for chloride and oxalate in rabbit ileal brush-border membrane vesicles.
abstract: To evaluate the possibility that an apical membrane conductive pathway for oxalate is present in the rabbit distal ileum, we studied oxalate ([14C]oxalate) and chloride (36Cl) uptake into brush-border membrane vesicles enriched 15- to 18-fold in sucrase activity. Voltage-sensitive pathways for oxalate and chloride were identified by the stimulation of uptake provided by an inwardly directed potassium diffusion potential in the presence of valinomycin. Additionally, outwardly directed oxalate (or chloride) gradients stimulated [14C]oxalate (or 36Cl) uptake to a greater degree in the absence of valinomycin (when intracellular and extracellular potassium are equal) than in the presence of valinomycin. Voltage-dependent anion uptake was poorly saturable: apparent affinity constants were 141 +/- 17 and 126 +/- 8 mM for chloride and oxalate, respectively. Activation energies for the voltage-dependent uptake processes were low: 4.7 and 6.3 kcal/mol for chloride and oxalate, respectively. Sensitivity profiles of voltage-dependent chloride and oxalate uptake to anion transport inhibitors were similar. We conclude that an anion conductance is present in the apical membranes of ileal enterocytes and that this conductance is a candidate pathway for oxalate efflux from the enterocyte during transepithelial oxalate secretion.
authors.affiliation: Division of Nephrology, Department of Medicine, University of California, Irvine, California 92717, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Freel
authors.forename: M
authors.initials: M
authors.lastname: Hatch
authors.forename: N D
authors.initials: ND
authors.lastname: Vaziri
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002250:Carbon Radioisotopes; D002712:Chlorides / Q000378:metabolism*; D002934:Cinnamates / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D007082:Ileum; D007413:Intestinal Mucosa / Q000502:physiology*; D007700:Kinetics; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D010070:Oxalates / Q000378:metabolism*; D011817:Rabbits; D013629:Tamoxifen / Q000494:pharmacology; D013696:Temperature; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D000838:Anions; D002250:Carbon Radioisotopes; D002712:Chlorides; D002934:Cinnamates; D010070:Oxalates; D013629:Tamoxifen; D014634:Valinomycin; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C061614:alpha-phenylcinnamate; D005947:Glucose; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid