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Chloride Conductance Determining Membrane Potential of Rabbit Articular Chondrocytes
Authors:K Tsuga  N Tohse  M Yoshino  T Sugimoto  T Yamashita  S Ishii  H Yabu
Institution:Department of Physiology, Sapporo Medical University School of Medicine, S-1 W-17 Chuo-Ku, Sapporo, 060-8556, Japan.
Abstract: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 potential shifted 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.
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