Chloride conductance determining membrane potential of rabbit articular chondrocytes.

Membrane conductance of cultured rabbit articular chondrocytes was characterized by means of the patch-clamp technique. The resting membrane potential of the articular chondrocytes was about -42 mV. The membrane potentialshifted in accordance with the prediction by the Nernst equation for Cl - when intracellular and extracellular concentrations of Cl - were changed. On the other hand, change in extracellular concentration of K + produced no shift in the membrane potential of chondrocytes. The Cl - channel blocker 4-acetamido-4'-isothiocyanatostilbene-2'2-disulfonic acid (SITS) depolarized the membrane potential. These findings suggest that the membrane potential of the chondrocytes is determined mainly by Cl - conductance. Using the cell-attached patch-clamp method, a large unitary conductance of 217 pS was observed in the articular chondrocytes. The unitary current was reversibly blocked by SITS. Therefore, the unitary current was carried by Cl - . The Cl - channel showed voltage-dependent activation and the channels exhibited long-lasting openings. Therefore, the membrane potential of rabbit cultured articular chondrocytes was mainly determined by the activities of the large-conductance and voltage-dependent Cl - channels.