KCl cotransport: A mechanism for basolateral chloride exit inNecturus gallbladder

Summary

K⁺ and Cl⁻-selective double-barreled microelectrodes were used to study the effect of changes in external K⁺ concentration on intracellular Cl⁻ activity (a ⁱ_Cl ) in epithelial cells ofNecturus gallbladder. Decreasing the K⁺ concentration simultaneously in both bathing solutions produced a decrease ina ⁱ_Cl . Steady-state values ofa ⁱ_Cl 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 ⁱ_Cl and Δμ_K appeared when the K⁺ concentration was changed in the serosal solution only. This indicates thata ⁱ_Cl depends on Δμ_K across the basolateral membrane.a ⁱ_Cl 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.