Molecular Pharmacology, Vol 10, 880-891, Copyright © 1974 by the American Society for Pharmacology and Experimental Therapeutics

Binding of Amiloride to Sodium Channels in Frog Skin

¹ Department of Pharmacology, University of Cambridge, England

Interactions between sodium ions and amiloride with the mucosal membrane have been studied using voltage-clamped frog skin. At sodium concentrations greater than 10 mEq/ liter the interactions of amiloride with the mucosal channels appear to be competitive and have a stoichiometry of 1:1. Binding of amiloride to sodium channels has been measured using [¹⁴C]amiloride. Reasonable agreement was found for the affinities of amiloride and triamterene derived from binding studies compared to values from inhibition studies. Antidiuretic hormone had no effect on the number of sodium channels in the mucosal surface of the skin, while the nominal currents passing the channels were doubled. The implications of the findings are discussed in relation to the mechanism by which antidiuretic hormone increases the mucosal permeability for sodium.

Note:
ACKNOWLEDGMENTS We are grateful to Merck Sharp & Dohme for a supply of [¹⁴C]amiloride and to Smith Kline & French for triamterene.