Isolated liver gap junctions: gating of transjunctional currents is similar to that in intact pairs of rat hepatocytes.

We have shown previously that conductance of rat liver gap junctions is blocked by an affinity-purified polyclonal antibody generated against rat liver junctional membranes, is not affected by moderate transjunctional or transmembrane potentials, and is reversibly decreased by cytoplasmic acidification and perfusion with octanol. We have now recorded currents from isolated liver gap junctions using patch electrodes dipped through a layer of mixed lipids whose concentrations match those of isolated liver appositional membranes. These currents are blocked by the same polyclonal antibody, are insensitive to moderate voltages imposed across the pipette tip, and are reversibly blocked by similar concentrations of H ions and octanol as are junctions in situ. The currents are likely to be gap junctional in origin; their block by low pH and other agents indicates that the gating mechanisms are intrinsic to the gap junctions themselves and presumably result from conformational change in the channel-forming protein.