A voltage-dependent K+ current contributes to membrane potential of acutely isolated canine articular chondrocytes.
The electrophysiological properties of acutely isolated canine articular chondrocytes have been characterized using patch-clamp methods. The 'steady-state' current-voltage relationship (I-V) of single chondrocytes over the range of potentials from -100 to +40 mV was highly non-linear, showing strong outward rectification positive to the zero-current potential. Currents activated at membrane potentials negative to -50 mV were time independent, and the I-V from -100 to -60 mV was linear, corresponding to an apparent input resistance of 9.3 +/- 1.4 G Omega (n= 23). The outwardly rectifying current was sensitive to the K(+) channel blocking ion tetraethylammonium (TEA), which had a 50% blocking concentration of 0.66 mM (at +50 mV). The 'TEA-sensitive' component of the outwardly rectifying current had time- and membrane potential-dependent properties, activated near -45 mV and was half-activated at -25 mV. The reversal potential of the 'TEA-sensitive' current with external K(+) concentration of 5 mm and internal concentration of 145 mM, was -84 mV, indicating that the current was primarily carried by K(+) ions. The resting membrane potential of isolated chondrocytes (-38.1 +/- 1.4 mV; n= 19) was depolarized by 14.8 +/- 0.9 mV by 25 mM TEA, which completely blocked the K(+) current of these cells. These data suggest that this voltage-sensitive K(+) channel has an important role in regulating the membrane potential of canine articular chondrocytes.
Wilson
Jim R
JR
Department of Civil Engineering and Joint Injury and Arthritis Research Group, The University of Calgary, Calgary, Alberta, Canada T2N 4N1.
Duncan
Neil A
NA
Giles
Wayne R
WR
Clark
Robert B
RB
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002358:Cartilage, Articular / Q000166:cytology / Q000502:physiology*; D002454:Cell Differentiation; D002469:Cell Separation; D018118:Chloride Channels / Q000187:drug effects; D019902:Chondrocytes / Q000502:physiology*; D004285:Dogs; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D018118:Chloride Channels; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds