K+ Secretion in Rat Distal Jejunum |
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Authors: | R. Cermak A. Evelgünne C. Lawnitzak E. Scharrer |
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Affiliation: | (1) Institute of Veterinary Physiology, University of Zurich, Winterthurerstrasse 260, CH-8057 Zurich, Switzerland, CH |
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Abstract: | The Ussing chamber technique was used to measure unidirectional Rb+ fluxes under short-circuit conditions across tissue sheets from proximal, central, and distal jejunum of rats. Whereas the proximal and central parts of the jejunum did not show any net transport of Rb+, there was a net secretion of around 0.2 μmol hr−1 cm−2 in the distal segment. This secretion could not be influenced significantly by mucosal application of K+ channel blockers such as Ba2+ (5 mm), tetraethylammonium (20 mm) or quinine (1 mm). Serosal ouabain (1 mm) blocked net secretion by increasing mucoserosal flux. Blockers of H+/K+ ATPases could not alter net fluxes of Rb+. Stimulation of Cl− secretion by forskolin (10 μm) or of Na+ absorption by serine (10 mm) failed to influence the observed secretion of Rb+. Adrenaline (10 μm) also had no effect on Rb+ fluxes. Blocking Na+/H+ exchange by 5-(N-Ethyl-N-isopropyl)-amilorid (100 μm) blocked net secretion by increasing mucoserosal flux, as did the addition of Na+ acetate (30 mm) to the mucosal solution. We conclude that the distal jejunum of the rat secretes K+ under short-circuit conditions. This secretion does not seem to occur via K+ channels, but through a pH dependent mechanism. Received: 16 February 1999/Revised: 29 June 1999 |
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Keywords: | : Potassium transport — K+/H+ exchange — Jejunum — Rat |
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