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Sodium transport systems in human chondrocytes. I. Morphological and functional expression of the Na+,K(+)-ATPase alpha and beta subunit isoforms in healthy and arthritic chondrocytes.

Trujillo, E, Alvarez de la Rosa, D, Mobasheri, A, Avila, J, González, T and Martín-Vasallo, P (1999) Sodium transport systems in human chondrocytes. I. Morphological and functional expression of the Na+,K(+)-ATPase alpha and beta subunit isoforms in healthy and arthritic chondrocytes. Histol Histopathol, 14 (4). pp. 1011-1022.

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Abstract

The chondrocyte is the cell responsible for the maintenance of the articular cartilage matrix. The negative charges of proteoglycans of the matrix draw cations, principally Na+, into the matrix to balance the negative charge distribution. The Na+,K(+)-ATPase is the plasma membrane enzyme that maintains the intracellular Na+ and K+ concentrations. The enzyme is composed of an alpha and a beta subunit, so far, 4 alpha and 3 beta isoforms have been identified in mammals. Chondrocytes are sensitive to their ionic and osmotic environment and are capable of adaptive responses to ionic environmental perturbations particularly changes to extracellular [Na+]. In this article we show that human fetal and adult chondrocytes express three alpha (alpha 1, alpha 2 and the neural form of alpha 3) and the three beta isoforms (beta 1, beta 2 and beta 3) of the Na+,K(+)-ATPase. The presence of multiple Na+,K(+)-ATPase isoforms in the plasma membrane of chondrocytes suggests a variety of kinetic properties that reflects a cartilage specific and very fine specialization in order to maintain the Na+/K+ gradients. Changes in the ionic and osmotic environment of chondrocytes occur in osteoarthritis and rheumatoid arthritis as result of tissue hydration and proteoglycan loss leading to a fall in tissue Na+ and K+ content. Although the expression levels and cellular distribution of the proteins tested do not vary, we detect changes in p-nitrophenylphosphatase activity "in situ" between control and pathological samples. This change in the sodium pump enzymatic activity suggests that the chondrocyte responds to these cationic environmental changes with a variation of the active isozyme types present in the plasma membrane.

Item Type: Article
Authors :
NameEmailORCID
Trujillo, EUNSPECIFIEDUNSPECIFIED
Alvarez de la Rosa, DUNSPECIFIEDUNSPECIFIED
Mobasheri, Aa.mobasheri@surrey.ac.ukUNSPECIFIED
Avila, JUNSPECIFIEDUNSPECIFIED
González, TUNSPECIFIEDUNSPECIFIED
Martín-Vasallo, PUNSPECIFIEDUNSPECIFIED
Date : October 1999
Uncontrolled Keywords : Adult, Animals, Arthritis, Rheumatoid, Biological Transport, Cartilage, Articular, Chondrocytes, Humans, Isoenzymes, Osteoarthritis, Rats, Sodium, Sodium-Potassium-Exchanging ATPase
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/827150

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