Benzamil sensitive ion channels contribute to volume regulation in canine chondrocytes

Lewis, R, Feetham, CH, Gentles, L, Penny, J, Tregilgas, L, Tohami, W, Mobasheri, A and Barrett-Jolley, R (2013) Benzamil sensitive ion channels contribute to volume regulation in canine chondrocytes BRITISH JOURNAL OF PHARMACOLOGY, 168 (7). pp. 1584-1596.

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Abstract

BACKGROUND AND PURPOSE: Chondrocytes exist within cartilage and serve to maintain the extracellular matrix. It has been postulated that osteoarthritic (OA) chondrocytes lose the ability to regulate their volume, affecting extracellular matrix production. In previous studies, we identified expression of epithelial sodium channels (ENaC) in human chondrocytes, but their function remained unknown. Although ENaC typically has Na(+) transport roles, it is also involved in the cell volume regulation of rat hepatocytes. ENaC is a member of the degenerin (Deg) family, and ENaC/Deg-like channels have a low conductance and high sensitivity to benzamil. In this study, we investigated whether canine chondrocytes express functional ENaC/Deg-like ion channels and, if so, what their function may be. EXPERIMENTAL APPROACH: Canine chondrocytes were harvested from dogs killed for unassociated welfare reasons. We used immunohistochemistry and patch-clamp electrophysiology to investigate ENaC expression and video microscopy to analyse the effects of pharmacological inhibition of ENaC/Deg on cell volume regulation. KEY RESULTS: Immunofluorescence showed that canine chondrocytes expressed ENaC protein. Single-channel recordings demonstrated expression of a benzamil-sensitive Na(+) conductance (9 pS), and whole-cell experiments show this to be approximately 1.5 nS per cell with high selectivity for Na(+) . Benzamil hyperpolarized chondrocytes by approximately 8 mV with a pD2 8.4. Chondrocyte regulatory volume decrease (RVI) was inhibited by benzamil (pD2 7.5) but persisted when extracellular Na(+) ions were replaced by Li(+) . CONCLUSION AND IMPLICATIONS: Our data suggest that benzamil inhibits RVI by reducing the influx of Na(+) ions through ENaC/Deg-like ion channels and present ENaC/Deg as a possible target for pharmacological modulation of chondrocyte volume.

Item Type:	Article
Divisions :	Faculty of Health and Medical Sciences > School of Veterinary Medicine
Authors :	Name Email ORCID Lewis, R Feetham, CH Gentles, L Penny, J Tregilgas, L Tohami, W Mobasheri, A Barrett-Jolley, R
Date :	1 April 2013
Identification Number :	10.1111/j.1476-5381.2012.02185.x
Uncontrolled Keywords :	Science & Technology, Life Sciences & Biomedicine, Pharmacology & Pharmacy, PHARMACOLOGY & PHARMACY, chondrocytes, electrophysiology, volume regulation, RVI, resting membrane potential, RMP, ENaC, BOVINE ARTICULAR CHONDROCYTES, EPITHELIAL NA+ CHANNEL, OSTEOARTHRITIC HUMAN CARTILAGE, SODIUM-CHANNELS, CELL-VOLUME, IN-SITU, INTRACELLULAR CALCIUM, RAT HEPATOCYTES, WATER-CONTENT, K+ CHANNELS
Related URLs :	Author
Additional Information :	Re-use of this article is permitted in accordance with the Terms and Conditions set out at http://wileyonlinelibrary.com/ onlineopen#OnlineOpen_Terms
Depositing User :	Symplectic Elements
Date Deposited :	23 Dec 2015 11:32
Last Modified :	31 Oct 2017 17:56
URI:	http://epubs.surrey.ac.uk/id/eprint/809553

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