Regulation of Na+, K+-ATPase density by the extracellular ionic and osmotic environment in bovine articular chondrocytes.
The abundance of Na+, K+-ATPase in cartilage is controlled by the ionic composition of the extracellular environment of chondrocytes, and specifically depends on the local concentration of polyanionic matrix proteoglycans. In this study, it was found that the plasma membrane density of Na+, K+-ATPase in isolated chondrocytes is sensitive to both ionic and osmotic changes in the extracellular environment. The upregulation observed experimentally was similar in magnitude as measured by 3H-ouabain binding, which indicates that chondrocytes respond adaptively to both ionic and osmotic stimuli. The precise mechanism for this novel mode of Na+, K+-ATPase regulation has yet to be elucidated. Physiological perturbation of the ionic and osmotic environment of chondrocytes may alter intracellular Na+ concentration and this may be one of a number of stimuli responsible for alterations to the expression and plasma membrane abundance of Na+, K+-ATPase in the cells.
Mobasheri
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Department of Biomedical Sciences, School of Biosciences, University of Westminster, London, United Kingdom. mobasha@westminster.ac.uk
D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology* / Q000201:enzymology; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000201:enzymology*; D003470:Culture Media / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism; D006982:Hypertonic Solutions / Q000494:pharmacology; D007552:Isotonic Solutions / Q000494:pharmacology; D009997:Osmotic Pressure; D015398:Signal Transduction / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D003470:Culture Media; D006982:Hypertonic Solutions; D007552:Isotonic Solutions; D000254:Sodium-Potassium-Exchanging ATPase