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BMC Research Notes

, 4:355

First Online: 13 September 2011Received: 23 August 2011Accepted: 13 September 2011DOI: 10.1186-1756-0500-4-355

Cite this article as: Yamazaki, M., Wu, T., Pondugula, S.R. et al. BMC Res Notes 2011 4: 355. doi:10.1186-1756-0500-4-355


BackgroundSodium absorption by semicircular canal duct SCCD epithelial cells is thought to contribute to the homeostasis of the volume of vestibular endolymph. It was previously shown that the epithelial cells could absorb Na under control of a glucocorticoid hormone dexamethasone and the absorptive transepithelial current was blocked by amiloride. The most commonly-observed target of amiloride is the epithelial sodium channel ENaC, comprised of the three subunits α-, β- and γ-ENaC. However, other cation channels have also been observed to be sensitive in a similar concentration range. The aim of this study was to determine whether SCCD epithelial cells absorb only Na or also K through an amiloride-sensitive pathway. Parasensory K absorption could contribute to regulation of the transduction current through hair cells, as found to occur via vestibular transitional cells S. H. Kim and D. C. Marcus. Regulation of sodium transport in the inner ear. Hear.Res. doi:10.1016-j.heares.2011.05.003, 2011.

ResultsWe determined the molecular and functional expression of candidate cation channels with gene array GEO GSE6197, whole-cell patch clamp and transepithelial recordings in primary cultures of rat SCCD. α-, β- and γ-ENaC were all previously reported as present. The selectivity of the amiloride-sensitive transepithelial and cell membrane currents was observed in Ussing chamber and whole-cell patch clamp recordings. The cell membrane currents were carried by Na but not K, but the Na selectivity disappeared when the cells were cultured on impermeable supports. Transepithelial currents across SCCD were also carried exclusively by Na.

ConclusionsThese results are consistent with the amiloride-sensitive absorptive flux of SCCD mediated by a highly Na-selective channel, likely αβγ-ENaC. These epithelial cells therefore absorb only Na via the amiloride-sensitive pathway and do not provide a parasensory K efflux from the canals via this pathway. The results further provide caution to the culture of epithelial cells on impermeable surfaces.

Electronic supplementary materialThe online version of this article doi:10.1186-1756-0500-4-355 contains supplementary material, which is available to authorized users.

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Autor: Muneharu Yamazaki - Tao Wu - Satyanarayana R Pondugula - Donald G Harbidge - Daniel C Marcus


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