Sodium and chloride absorptive defects in the small intestine in Slc26a6 null mice

U Seidler, I Rottinghaus, J Hillesheim, M Chen… - … -European Journal of …, 2008 - Springer
U Seidler, I Rottinghaus, J Hillesheim, M Chen, B Riederer, A Krabbenhöft, R Engelhardt…
Pflügers Archiv-European Journal of Physiology, 2008Springer
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 …
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 36Cl and 22Na+ 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.
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