AJP - Cell Physiology, Vol 270, Issue 5 C1300-C1310, Copyright © 1996 by American Physiological Society

ARTICLES

Pathways for K+ transport across the bovine articular chondrocyte membrane and their sensitivity to cell volume

A. C. Hall, I. Starks, C. L. Shoults and S. Rashidbigi
University Laboratory of Physiology, Oxford, United Kingdom.

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.

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