title: Barium inhibition of sodium ion transport in toad bladder.
abstract: The effect of Ba2+ on Na+ transport and electrical characteristics of toad bladder was determined from change produced in short circuit current (Isc), epithelial, apical and basal-lateral potentials (psit, psia, psib), epithelial and membrane resistances (Rt, Ra, Rb) and shunt resistance (Rs). Mucosal Ba2+ had no effect. Serosal Ba2+ reduced Isc, psit, psia, and psib, but had no effect on Rt, Ra, Rb and Rs. Minimal effective Ba2+ concentration was 5-10(-5) M. The phenomenon was reversed by Ba2+ removal, but not by 86 mM serosal K+. Ba2+ inhibition of Isc did not impair the response to vasopressin which was quantitatively the same as controls. Psia with Ba2+ equalled psib. After Ba2+ inhibition, ouabain produced no further decrease in psit and Isc. Ba2+ exposure after ouabain did not decrease psit and Isc. The results suggest that Ba2+ inhibits the basal-lateral electrogenic Na+ pump.
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology*; D001693:Biological Transport, Active; D002024:Bufo marinus; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D003864:Depression, Chemical; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism*; D014667:Vasopressins / Q000494:pharmacology
chemical_list: D014667:Vasopressins; D001464:Barium; D010042:Ouabain; D012964:Sodium