Cl− transport in basolateral renal medullary vesicles: II. Cl− channels in planar lipid bilayers

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Abstract
The present studies examined some of the properties of Cl− channels in renal outer medullary membrane vesicles incorporated into planar lipid bilayers. The predominant channel was anion selective having aP Cl/P K ratio of 10 and a unit conductance of 93 pS in symmetric 320mm KCl. In asymmetric KCl solutions, theI-V relations conformed to the Goldman-Hodgkin-Katz equation. Channel activity was voltage-dependent with a gating charge of unity. This voltage dependence of channel activity may account, at least in part, for the striking voltage dependence of the basolateral membrane Cl− conductance of isolated medullary thick ascending limb segments. The Cl− channels incorporated into the planar bilayers were asymmetrical: thetrans surface was sensitive to changes in ionized Ca2+ concentrations and insensitive to reducing KCl concentrations to 10mm, while thecis side was insensitive to changes in ionized Ca2+ concentrations, but was inactivated by reducing KCl concentrations to 50mm.