Chloride flux in bilayer membranes: the electrically silent chloride flux in semispherical bilayers

High resistance semispherical bilayer membranes of areas as large as 0.3 cm-2 were formed from a decane solution of synthetic diphytanoylphosphatidylcholine. These bilayers had a specific resistance of about 10-9 omega cm-2 and a specific capacitance of 0.38 mu F cm- minus 2 at 20 degrees in 0.1 M KCL. Under these conditions, chloride permeability was 6.8 times 10- minus 8 cm/sec. This electrically silen 36-Cl flux was found to be about 10-3-fold larger than the chloride current calculated from the electrical parameters of the system. The chloride flux in the bilayer was independent of the applied electrical field and was unaltered by addition of reducing agents to the ambient aqueous solutions. It was, however, substantially reduced when NO3 minus was substituted for Cl minus on the side of the bilayer initially free of 36-Cl, or if I minus was added to the aquesous phases in the concentration range of 0.001-0.1 M. These results strongly suggested that the electrically silent flux of 36-Cl is primarily a carrier mediated diffusion process in which phosphatidylcholine acts as the carrier species.