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A voltage-dependent K+ current contributes to membrane potential of acutely isolated canine articular chondrocytes

By Jim R Wilson, Neil A Duncan, Wayne R Giles and Robert B Clark

Abstract

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 GΩ (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

Topics: Research Papers
Publisher: Blackwell Science Inc
OAI identifier: oai:pubmedcentral.nih.gov:1665044
Provided by: PubMed Central
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