Barium inhibition of sodium ion transport in toad bladder |
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| Authors: | A.G. Ramsay D.L. Gallagher R.L. Shoemaker G. Sachs |
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| Affiliation: | 1. Department of Medicine, College of Physicians and Surgeons Columbia University (Mary Imogene Bassett Hospital, Cooperstown, New York), New York, N.Y. U.S.A.;2. Departments of Physiology and Membrane Biology, University of Alabama, Birmingham, Ala. U.S.A. |
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| 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 (ψt, ψa, ψb), epithelial and membrane resistances (Rt, Ra, Rb) and shunt resistance (Rs). Mucosal Ba2+ had no effect. Serosal Ba2+ reduced Isc, ψt, ψa, and ψb, 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. ψa with Ba2+ equalled ψb. After Ba2+ inhibition, ouabain produced no further decrease in ψt and Isc. Ba2+ exposure after ouabain did not decrease ψt and Isc. The results suggest that Ba2+ inhibits the basal-lateral electrogenic Na+ pump. |
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