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Sodium transfer from endolymph through a luminal amiloride-sensitive channel
E Ferrary1, C Bernard, O Oudar
1Department of Physiology, Faculté Xavier Bichat, Université Paris, Institut National de la Santé et de la Recherche Médicale U.251, France.
The American Journal of Physiology
|August 1, 1989
Summary
This study reveals frog semicircular canal preparations can secrete potassium and absorb sodium, maintaining inner ear fluid balance. An amiloride-sensitive sodium channel in the ampulla is key for endolymph secretion.
Area of Science:
- Physiology
- Otolaryngology
- Cell Biology
Background:
- The labyrinthine epithelium of the semicircular canal regulates the electrochemical composition of inner ear fluids.
- Understanding sodium (Na) and potassium (K) transport mechanisms is crucial for inner ear homeostasis.
Purpose of the Study:
- To develop an in vitro frog semicircular canal preparation to investigate Na transport across the labyrinthine epithelium.
- To identify the specific mechanisms and pathways involved in endolymph secretion.
Main Methods:
- An isolated frog semicircular canal preparation was utilized.
- Perilymph-like and endolymph-like solutions were applied to the lumen.
- Net and unidirectional Na fluxes were measured with and without transport inhibitors (amiloride, ouabain, furosemide, bumetanide).
Main Results:
- The preparation secreted K and absorbed Na, generating a lumen-positive potential.
- Amiloride significantly inhibited unidirectional Na efflux from the endolymph, increasing net Na influx.
- Abluminal ouabain, furosemide, and bumetanide also increased net Na flux.
Conclusions:
- The isolated frog semicircular canal is a valid model for studying endolymph secretion.
- Endolymph secretion primarily occurs in the ampulla.
- An apical amiloride-sensitive Na channel facilitates Na transfer out of endolymph, driven by Na+-K+-ATPase activity.