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Immunologic and autoradiographic localisation of the Na+, K(+)-ATPase in articular cartilage: upregulation in response to changes in extracellular Na+ concentration.

Mobasheri, A, Hall, AC, Urban, JP, France, SJ and Smith, AL (1997) Immunologic and autoradiographic localisation of the Na+, K(+)-ATPase in articular cartilage: upregulation in response to changes in extracellular Na+ concentration. Int J Biochem Cell Biol, 29 (4). pp. 649-657.

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Abstract

The maintenance of a relatively low intracellular Na+:K+ ratio is essential for the functioning of a wide range of cellular processes, and is achieved principally by the activity of the membrane-bound Na+, K(+)-ATPase. Chondrocytes, the cells of articular cartilage, exist in an ionic environment where the free extracellular [Na+] is higher (250-400 mM) than that of most other tissues (approximately 140 mM) owing to the fixed negative charges on glycosaminoglycans in the extracellular matrix. This can increase further during static joint loading when fluid expression occurs. To determine aspects of how chondrocytes regulate their ionic composition, in this study, the in situ distribution, pattern of isoform expression and density of the Na+, K(+)-ATPase within cartilage has been investigated. The density of the Na+, K(+)-ATPase was found to be high in the mid-zone, but lower in the surface and deep zones. Immunofluorescence microscopy using monoclonal antibodies to the catalytic alpha subunits of the Na+, K(+)-ATPase revealed the expression of isoforms alpha 1 and alpha 3. Alterations to the extracellular [Na+] (from 80-220 mM, or 120-220 mM) significantly elevated Na+, K(+)-ATPase density of in situ chondrocytes. The results indicate that the Na+, K(+)-ATPase is abundantly expressed in articular chondrocytes and its density is sensitive to the extracellular [Na+]. The expression of the alpha 3 isoform is surprising for a non-neuronal cell, and may indicate a physiological adaptation to the unusually high extracellular [Na+] to which chondrocytes are exposed in the extracellular matrix of cartilage.

Item Type: Article
Authors :
NameEmailORCID
Mobasheri, Aa.mobasheri@surrey.ac.ukUNSPECIFIED
Hall, ACUNSPECIFIEDUNSPECIFIED
Urban, JPUNSPECIFIEDUNSPECIFIED
France, SJUNSPECIFIEDUNSPECIFIED
Smith, ALUNSPECIFIEDUNSPECIFIED
Date : April 1997
Uncontrolled Keywords : Animals, Autoradiography, Cartilage, Articular, Cattle, Chondrocytes, Extracellular Space, Microscopy, Fluorescence, Sodium, Sodium-Potassium-Exchanging ATPase, Up-Regulation
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 17 May 2017 10:17
Last Modified : 17 May 2017 14:48
URI: http://epubs.surrey.ac.uk/id/eprint/827156

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