title: Sodium and chloride absorptive defects in the small intestine in Slc26a6 null mice.
abstract: PAT1 (Slc26a6) is located on the apical membrane of the small intestinal villi, but its role for salt absorption has not been studied. To ascertain the role of Slc26a6 in jejunal sodium and chloride absorption, and its interplay with NHE3, muscle-stripped jejuna from Slc26a6+/+ and -/- and NHE3 +/+ and -/- mice were mounted in Ussing chambers and electrical parameters, and (36)Cl(-) and (22)Na(+) fluxes were measured. In parallel studies, expression of the apical Na(+)/H(+) exchanger (NHE3) was examined by immunofluorescence labeling and immunoblot analysis in brush border membrane (BBM). In the basal state, net Cl(-) and Na(+) fluxes were absorptive in Slc26a6-/- and +/+ jejuni, but significantly decreased in -/- animals. Upon forskolin addition, net Na(+) absorption decreased, Isc strongly increased, and net Cl(-) flux became secretory in Slc26a6-/- and +/+ jejuni. When luminal glucose was added to activate Na(+)/glucose cotransport, concomitant Cl(-) absorption was significantly reduced in Slc26a6 -/- jejuni, while Na(+) absorption increased to the same degree in Slc26a6 -/- and +/+ jejuni. Identical experiments in NHE3-deficient jejuni also showed reduced Na(+) and Cl(-) absorption. Results further demonstrated that the lack of NHE3 rendered Na(+) and Cl(-) absorption unresponsive to inhibition by cAMP, but did not affect glucose-driven Na(+) and Cl(-) absorption. Immunoblotting revealed comparable NHE3 abundance and distribution in apical membranes in Slc26a6-/- and +/+ mice. The data strongly suggests that Slc26a6 acts in concert with NHE3 in electroneutral salt absorption in the small intestine. Slc26a6 also serves to absorb Cl(-) during glucose-driven salt absorption.
authors.affiliation: Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany. seidler.ursula@mh-hannover.de
authors.forename: Ursula
authors.initials: U
authors.lastname: Seidler
authors.forename: Ingrid
authors.initials: I
authors.lastname: Rottinghaus
authors.forename: Jutta
authors.initials: J
authors.lastname: Hillesheim
authors.forename: Mingmin
authors.initials: M
authors.lastname: Chen
authors.forename: Brigitte
authors.initials: B
authors.lastname: Riederer
authors.forename: Anja
authors.initials: A
authors.lastname: Krabbenhöft
authors.forename: Regina
authors.initials: R
authors.lastname: Engelhardt
authors.forename: Martin
authors.initials: M
authors.lastname: Wiemann
authors.forename: Zhaouhui
authors.initials: Z
authors.lastname: Wang
authors.forename: Sharon
authors.initials: S
authors.lastname: Barone
authors.forename: Michael P
authors.initials: MP
authors.lastname: Manns
authors.forename: Manoocher
authors.initials: M
authors.lastname: Soleimani
mesh_terms: D000818:Animals; D017920:Antiporters / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D020895:Enterocytes / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008871:Microvilli / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D012979:Sodium Radioisotopes; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D000076988:Sulfate Transporters
chemical_list: D017920:Antiporters; D002712:Chlorides; C466900:Slc26a6 protein, mouse; C000613386:Slc9a3 protein, mouse; D012979:Sodium Radioisotopes; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D000076988:Sulfate Transporters; D005576:Colforsin; D012964:Sodium; D005947:Glucose