Pathways for K+ transport across the bovine articular chondrocyte membrane and their sensitivity to cell volume.
The contributions of various K+ transport pathways in bovine chondrocytes isolated from articular cartilage and their responses to changes in cell volume have been studied. K+(86Rb+) uptake mediated by the Na(+)-K(+) pump and Na(+)-K(+)-2Cl- cotransporter were stimulated by cell shrinkage, the latter as part of the regulatory volume increases (RVI) response, the former as an indirect effect resulting from the rise in intracellular Na+ concentration during RVI. For both transporters, there was an increase in the maximum velocity with no detectable effect on the Michaelis constant. There was no evidence for volume-sensitive K+ transport mediated by the K(+)-Cl- cotransporter, or Ca(2+)-activated K+ channels. However, chondrocyte swelling stimulated a ouabain- and bumetanide-insensitive K+ flux sensitive to pimozide and other drugs, which exhibited some of the properties of the relatively nonspecific volume-sensitive "osmolyte" channel described in other cell types.
Hall
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AC
University Laboratory of Physiology, Oxford, United Kingdom.
Starks
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I
Shoults
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CL
Rashidbigi
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S
D000818:Animals; D001692:Biological Transport; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism*; D002417:Cattle; D002469:Cell Separation; D003470:Culture Media; D008297:Male; D009994:Osmolar Concentration; D009997:Osmotic Pressure; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000493:pharmacokinetics*; D015221:Potassium Channels / Q000502:physiology; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002352:Carrier Proteins; D003470:Culture Media; D015221:Potassium Channels; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D002118:Calcium