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Benzamil sensitive ion channels contribute to volume regulation in canine chondrocytes
Author(s) -
Lewis R,
Feetham CH,
Gentles L,
Penny J,
Tregilgas L,
Tohami W,
Mobasheri A,
BarrettJolley R
Publication year - 2013
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2012.02185.x
Subject(s) - epithelial sodium channel , extracellular , ion channel , chemistry , sodium channel , patch clamp , microbiology and biotechnology , chondrocyte , electrophysiology , medicine , sodium , endocrinology , biophysics , biology , in vitro , biochemistry , receptor , organic chemistry
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 N a + transport roles, it is also involved in the cell volume regulation of rat hepatocytes. ENaC is a member of the degenerin ( D eg) family, and ENaC / D eg‐like channels have a low conductance and high sensitivity to benzamil. In this study, we investigated whether canine chondrocytes express functional ENaC / D eg‐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 / D eg on cell volume regulation. Key Results Immunofluorescence showed that canine chondrocytes expressed ENaC protein. Single‐channel recordings demonstrated expression of a benzamil‐sensitive N a + conductance (9 pS ), and whole‐cell experiments show this to be approximately 1.5 nS per cell with high selectivity for N a + . Benzamil hyperpolarized chondrocytes by approximately 8 mV with a pD 2 8.4. Chondrocyte regulatory volume decrease ( RVI ) was inhibited by benzamil ( pD 2 7.5) but persisted when extracellular N a + ions were replaced by L i + . Conclusion and Implications Our data suggest that benzamil inhibits RVI by reducing the influx of N a + ions through ENaC / D eg‐like ion channels and present ENaC / D eg as a possible target for pharmacological modulation of chondrocyte volume.