KCl cotransport: A mechanism for basolateral chloride exit inNecturus gallbladder

Abstract

K⁺ and Cl⁻-selective double-barreled microelectrodes were used to study the effect of changes in external K⁺ concentration on intracellular Cl⁻ activity (a _Cl ⁱ ) in epithelial cells ofNecturus gallbladder. Decreasing the K⁺ concentration simultaneously in both bathing solutions produced a decrease ina _Cl ⁱ . Steady-state values ofa _Cl ⁱ were related to the values of the chamical potential gradient for K⁺ (Δμ_K) across either the apical or the basolateral cell membrane. A similar dependence betweena _Cl ⁱ and Δμ_K appeared when the K⁺ concentration was changed in the serosal solution only. This indicates thata _Cl ⁱ depends on Δμ_K across the basolateral membrane.a _Cl ⁱ was virtually independent of the membrane potential. This supports the idea that both the mucosal and the basolateral membranes ofNecturus gallbladder cells have very low passive permeabilities to Cl⁻. These results indicate that the exit of Cl⁻ fromNecturus gallbladder cells is driven by Δμ_K across the basolateral membrane, and suggest that a KCl electroneutral coupled mechanism in this membrane plays an important role in transcellular Cl⁻ transport.