Molecular Pharmacology, Vol 10, 892-903, Copyright © 1974 by the American Society for Pharmacology and Experimental Therapeutics

Interactions of Sodium Channels in Transporting Epithelia: a Two-State Model

¹ Department of Pharmacology, University of Cambridge, England

A two-state (allosteric) model based on that for allosteric proteins is proposed for the sodium ion-translocating mechanism of transporting epithelia. The model supposes that the mechanism can exist in two alternative configurations: one form which can translocate sodium ions through the cell membrane, and another form which is unable to do this. Interactions between a number of substances which either increase or decrease sodium fluxes through the mucosal membranes are considered in terms of the model. The behavior of the model was found to mirror that of actual epithelia for a number of experimental situations. At the present time the following interactions with the translocation mechanism can be best explained in terms of the two-state model: amiloride-Na⁺, amiloride-Na⁺-antidiuretic hormone, Ca⁺, Ca⁺⁺-antidiuretic hormone, and Ca⁺⁺-amiloride.

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ACKNOWLEDGMENT My thanks to Drs. J. and B. Maetz for hospitality during part of this work.