Sodium selectivity of Reissner's membrane epithelial cells.

{"sci_version": "1.0", "schema": "https://corpus.bntrg.co.uk/sci/1.0/sci.schema.json", "id": "pmid:21284860", "kind": "science-record", "revision": 5, "content_hash": "sha256:bc72fdf5469c3f99a8456a66213928e66bacbcbd2fd247032cf92daeea598052", "created_at": "2026-11-01T15:14:34Z", "updated_at": "2026-11-01T21:19:36Z", "generator": {"name": "corpus-assay-engine", "run_id": "reading-sci-2026-11-01"}, "paper": {"state": "complete", "title": "Sodium selectivity of Reissner's membrane epithelial cells.", "doi": "10.1186/1472-6793-11-4", "pmid": "21284860", "authors": ["Muneharu Yamazaki", "Kyunghee X Kim", "Daniel C Marcus"], "journal": "BMC physiology", "year": 2011, "abstract": "BACKGROUND: Sodium absorption by Reissner's membrane is thought to contribute to the homeostasis of the volume of cochlear endolymph. It was previously shown that the absorptive transepithelial current was blocked by amiloride and benzamil. The most commonly-observed target of these drugs is the epithelial sodium channel (ENaC), which is composed of the three subunits α-,β- and γ-ENaC. However, other less-selective cation channels have also been observed to be sensitive to benzamil and amiloride. The aim of this study was to determine whether Reissner's membrane epithelial cells could support parasensory K+ absorption via amiloride- and benzamil-sensitive electrogenic pathways.\nRESULTS: We determined the molecular and functional expression of candidate cation channels with gene array (GEO GSE6196), RT-PCR, and whole-cell patch clamp. Transcript expression analysis of Reissner's membrane detected no amiloride-sensitive acid-sensing ion channels (ASIC1a, ASIC2a, ASIC2b) nor amiloride-sensitive cyclic-nucleotide gated channels (CNGA1, CNGA2, CNGA4, CNGB3). By contrast, α-,β- and γ-ENaC were all previously reported as present in Reissner's membrane. The selectivity of the benzamil-sensitive cation currents was observed in whole-cell patch clamp recordings under Cl--free conditions where cations were the only permeant species. The currents were carried by Na+ but not K+, and the permeability of Li+ was greater than that of Na+ in Reissner's membrane. Complete replacement of bath Na+ with the inpermeable cation NMDG+ led to the same inward current as with benzamil in a Na+ bath.\nCONCLUSIONS: These results are consistent with the amiloride/benzamil-sensitive absorptive flux of Reissner's membrane mediated by a highly Na+-selective channel that has several key characteristics in common with αβγ-ENaC. The amiloride-sensitive pathway therefore absorbs only Na+ in this epithelium and does not provide a parasensory K+ efflux route from scala media.", "claims": [{"id": "claim-method", "statement": "Increases and decreases in current and conductance were determined by Student's paired or unpaired t-test as appropriate for the specific data sets.", "kind": "methodological", "target": null, "evidence": [{"asset": "source:pmid:21284860", "locator": "sections[15] \"Statistical analysis\" paragraph 2", "quote": "Increases and decreases in current and conductance were determined by Student's paired or unpaired t-test as appropriate for the specific data sets."}], "state": "complete"}, {"id": "claim-data-access", "statement": "Several isoforms of acid-sensitive ion channels (ASIC) and cyclic-nucleotide gated (CNG) channels were listed in our gene array of mouse Reissner's membrane (GEO GSE6196; Table 2) [6].", "kind": "methodological", "target": null, "evidence": [{"asset": "source:pmid:21284860", "locator": "sections[4] \"Expression of benzamil-sensitive cation channels in RM\" paragraph 2", "quote": "Several isoforms of acid-sensitive ion channels (ASIC) and cyclic-nucleotide gated (CNG) channels were listed in our gene array of mouse Reissner's membrane (GEO GSE6196; Table 2) [6]."}], "state": "complete"}], "gaps": []}, "experiment": {"state": "partial", "objective": null, "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:21284860"], "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": "blocked", "blocked_on": "data:accession_absent", "description": "The GEO series accession resolves and its sample accessions are listed. 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