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 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.
Tsuga
K
K
Department of Physiology, Sapporo Medical University School of Medicine, S-1 W-17 Chuo-Ku, Sapporo, 060-8556, Japan.
Tohse
N
N
Yoshino
M
M
Sugimoto
T
T
Yamashita
T
T
Ishii
S
S
Yabu
H
H
D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000502:physiology; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D002713:Chlorine / Q000378:metabolism; D019902:Chondrocytes / Q000187:drug effects / Q000502:physiology*; D004553:Electric Conductivity; D006614:Hindlimb; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D012782:Shoulder
D018118:Chloride Channels; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D002713:Chlorine; D011188:Potassium