Basolateral potassium channel in turtle colon. Evidence for single-file ion flow.

Abstract

Treatment of the apical surface of the isolated, ouabain-inhibited turtle colon with the polyene antibiotic amphotericin B permitted the properties of a Ba-sensitive K conductance in the basolateral membrane to be discerned from the measurements of transepithelial fluxes and electrical currents. Simultaneous measurements of K currents and 42K fluxes showed that the movement of K was not in accord with simple diffusion. Two other cations, Tl and Rb, were also permeable and, in addition, exhibited strong interactions with the K tracer fluxes. Permeant cations exhibit positive coupling, which is consistent with a single-file mechanism of ion translocation through a membrane channel.