Sodium selectivity of semicircular canal duct epithelial cells.

{"sci_version": "1.2", "schema": "https://corpus.bntrg.co.uk/sci/1.0/sci.schema.json", "id": "pmid:21914199", "kind": "science-record", "revision": 5, "content_hash": "sha256:bd2493314bf43191e48b54b272ced7c62fa9ca81c377751ff7133a1f148d15bd", "created_at": "2026-11-01T15:40:02Z", "updated_at": "2026-11-01T21:19:38Z", "generator": {"name": "corpus-assay-engine", "run_id": "reading-sci-2026-11-01"}, "paper": {"state": "complete", "title": "Sodium selectivity of semicircular canal duct epithelial cells.", "doi": "10.1186/1756-0500-4-355", "pmid": "21914199", "authors": ["Muneharu Yamazaki", "Tao Wu", "Satyanarayana R Pondugula", "Donald G Harbidge", "Daniel C Marcus"], "journal": "BMC research notes", "year": 2011, "abstract": "BACKGROUND: Sodium 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].\nRESULTS: We 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+.\nCONCLUSIONS: These 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.", "claims": [{"id": "claim-method", "statement": "The significance of increases and decreases in current were determined by Student's paired or unpaired t-test.", "kind": "methodological", "target": null, "evidence": [{"asset": "source:pmid:21914199", "locator": "sections[22] \"Statistical analysis\" paragraph 3", "quote": "The significance of increases and decreases in current were determined by Student's paired or unpaired t-test."}], "state": "complete"}, {"id": "claim-data-access", "statement": "Our methodology conforms to the MIAME (Minimum Information about a Microarray Experiment) guidelines and details are deposited with the data in [GEO: GSE6197] [6].", "kind": "methodological", "target": null, "evidence": [{"asset": "source:pmid:21914199", "locator": "sections[21] \"Gene array analysis\" paragraph 2", "quote": "Our methodology conforms to the MIAME (Minimum Information about a Microarray Experiment) guidelines and details are deposited with the data in [GEO: GSE6197] [6]."}], "state": "complete"}, {"id": "claim-target-result", "statement": "The study found that amiloride-sensitive currents in SCCD epithelial cells on permeable supports were highly selective for Na+ and did not carry K+; statistical significance was assessed with paired or unpaired Student's t-tests at P < 0.05, and gene-array source details were deposited in GEO GSE6197.", "kind": "quantitative", "target": {"value": 0.05, "unit": "p-value", "tolerance": null, "source": "The significance of increases and decreases in current were determined by Student's paired or unpaired t-test. Differences were considered statistically significant at a level of P < 0.05 (Microsoft Excel)."}, "evidence": [{"asset": "source:pmid:21914199", "locator": "sections[0] \"Abstract\" paragraph 2", "quote": "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+."}, {"asset": "source:pmid:21914199", "locator": "sections[22] \"Statistical analysis\" paragraph 3", "quote": "The significance of increases and decreases in current were determined by Student's paired or unpaired t-test. Differences were considered statistically significant at a level of P < 0.05 (Microsoft Excel)."}, {"asset": "source:pmid:21914199", "locator": "sections[21] \"Gene array analysis\" paragraph 2", "quote": "Our methodology conforms to the MIAME (Minimum Information about a Microarray Experiment) guidelines and details are deposited with the data in [GEO: GSE6197] [6]."}], "state": "complete"}], "gaps": []}, "experiment": {"state": "complete", "objective": "The study found that amiloride-sensitive currents in SCCD epithelial cells on permeable supports were highly selective for Na+ and did not carry K+; statistical significance was assessed with paired or unpaired Student's t-tests at P < 0.05, and gene-array source details were deposited in GEO GSE6197.", "steps": [{"id": "read_published_estimate", "order": 1, "name": "Read the published estimate from the source", "kind": "other", "state": "complete", "blocked_on": null, "description": "The claim, method and evidence span published with the source article.", "duration_hours": null, "parameters": {}, "inputs": ["source:pmid:21914199"], "outputs": ["the published estimate and its evidence"], "instruments": [], "reagents": []}, {"id": "obtain_source_data", "order": 2, "name": "Obtain the source data from the named repository", "kind": "data-preparation", "state": "complete", "blocked_on": null, "description": "The GEO series accession resolves and its sample accessions are listed. 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