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Secretion of endolymph by semicircular canals of the shark.
Am J Physiol. 1988 Oct; 255(4 Pt 2):F711-9.AJ

Abstract

The semicircular canals of the vestibular labyrinth of the dogfish shark, Squalus acanthias, may serve as a simple in vitro system for the study of the ionic transport mechanisms involved in endolymph formation. Electron microscopy showed that the epithelium was made up of at least three distinct cell types divided into separate regions running the length of the canals. Secretion of endolymph was studied in isolated canals by the split droplet method; when the lumens of the canals were filled with shark Ringer a potassium-rich fluid was secreted into the lumen at a rate of 0.34 microliter.cm-2.min-1. The K concentration of the secreted fluid averaged 112 mM; the calculated rate of K secretion was 2.3 mumol.cm-2.h-1, comparable to recent measurements in mammalian utricle. Fluid secretion was dependent on active transport and was inhibited by ouabain, bumetanide, or methazolamide in the external bathing solution. Fluid secretion was unaffected by the K channel blocker, Ba, in the luminal droplet or by the adenylate cyclase stimulator, forskolin, in the external bathing solution. For electrophysiological analysis, isolated canals were perfused in a chamber designed for voltage/current clamping; an axial wire was inserted into the canal lumen and constant-current pulses were passed to determine tissue resistance. When the luminal fluid was high-K Ringer, transepithelial potential difference was -1.1 mV (lumen negative) and resistance 37 omega.cm2. Dilution and bi-ionic potential measurements showed that the epithelium of the canals exhibited only slight cation selectivity. These results are consistent with a model for endolymph secretion involving cotransport secondary to the ion gradients created by the Na+-K+-ATPase.

Authors+Show Affiliations

Laboratory of Kidney and Electrolyte Metabolism, National Institutes of Health, Bethesda, Maryland 20892.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

3177654

Citation

Garvin, J L., et al. "Secretion of Endolymph By Semicircular Canals of the Shark." The American Journal of Physiology, vol. 255, no. 4 Pt 2, 1988, pp. F711-9.
Garvin JL, Spring KR, Santi PA. Secretion of endolymph by semicircular canals of the shark. Am J Physiol. 1988;255(4 Pt 2):F711-9.
Garvin, J. L., Spring, K. R., & Santi, P. A. (1988). Secretion of endolymph by semicircular canals of the shark. The American Journal of Physiology, 255(4 Pt 2), F711-9.
Garvin JL, Spring KR, Santi PA. Secretion of Endolymph By Semicircular Canals of the Shark. Am J Physiol. 1988;255(4 Pt 2):F711-9. PubMed PMID: 3177654.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Secretion of endolymph by semicircular canals of the shark. AU - Garvin,J L, AU - Spring,K R, AU - Santi,P A, PY - 1988/10/1/pubmed PY - 1988/10/1/medline PY - 1988/10/1/entrez SP - F711 EP - 9 JF - The American journal of physiology JO - Am. J. Physiol. VL - 255 IS - 4 Pt 2 N2 - The semicircular canals of the vestibular labyrinth of the dogfish shark, Squalus acanthias, may serve as a simple in vitro system for the study of the ionic transport mechanisms involved in endolymph formation. Electron microscopy showed that the epithelium was made up of at least three distinct cell types divided into separate regions running the length of the canals. Secretion of endolymph was studied in isolated canals by the split droplet method; when the lumens of the canals were filled with shark Ringer a potassium-rich fluid was secreted into the lumen at a rate of 0.34 microliter.cm-2.min-1. The K concentration of the secreted fluid averaged 112 mM; the calculated rate of K secretion was 2.3 mumol.cm-2.h-1, comparable to recent measurements in mammalian utricle. Fluid secretion was dependent on active transport and was inhibited by ouabain, bumetanide, or methazolamide in the external bathing solution. Fluid secretion was unaffected by the K channel blocker, Ba, in the luminal droplet or by the adenylate cyclase stimulator, forskolin, in the external bathing solution. For electrophysiological analysis, isolated canals were perfused in a chamber designed for voltage/current clamping; an axial wire was inserted into the canal lumen and constant-current pulses were passed to determine tissue resistance. When the luminal fluid was high-K Ringer, transepithelial potential difference was -1.1 mV (lumen negative) and resistance 37 omega.cm2. Dilution and bi-ionic potential measurements showed that the epithelium of the canals exhibited only slight cation selectivity. These results are consistent with a model for endolymph secretion involving cotransport secondary to the ion gradients created by the Na+-K+-ATPase. SN - 0002-9513 UR - https://www.unboundmedicine.com/medline/citation/3177654/Secretion_of_endolymph_by_semicircular_canals_of_the_shark_ L2 - http://journals.physiology.org/doi/full/10.1152/ajprenal.1988.255.4.F711?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -