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Endolymphatic sodium homeostasis by Reissner's membrane
1Kansas State University, Department of Anatomy and Physiology, 126 Coles Hall, 1600 Denison Ave., Manhattan, KS 66506-5802, USA.
Neuroscience
|May 24, 2003
Summary
Reissner's membrane absorbs sodium ions (Na+) from cochlear endolymph, crucial for hearing. This study confirms Reissner's membrane's role in maintaining cochlear fluid balance and function.
Area of Science:
- Oto-rhino-laryngology
- Cell Physiology
- Membrane Transport
Background:
- Cochlear sensory transduction relies on active sodium ion (Na+) extrusion from endolymph.
- Reissner's membrane forms a critical barrier between cochlear endolymph and perilymph.
Purpose of the Study:
- To investigate the role of Reissner's membrane in cochlear sodium ion (Na+) transport.
- To determine if Reissner's membrane contributes to the active extrusion of Na+ from endolymph.
Main Methods:
- Isolated gerbil Reissner's membrane was used to measure short-circuit current (I(sc)).
- The effects of amiloride analogs, Na(+),K(+)-ATPase inhibitors (ouabain), and potassium channel blockers (Ba2+, 4-aminopyridine, quinine) on I(sc) were assessed.
- Inhibition by bumetanide and effects of forskolin and genistein were also examined.
Main Results:
- Reissner's membrane exhibited a short-circuit current (I(sc)) indicative of cation absorption.
- I(sc) was significantly inhibited by amiloride analogs, suggesting Na+ absorption via epithelial sodium channels.
- Ouabain and specific K+ channel blockers inhibited I(sc), indicating the presence of a voltage-activated K+ channel.
Conclusions:
- Reissner's membrane actively absorbs sodium ions (Na+) from the cochlear endolymph.
- This Na+ absorption by Reissner's membrane is a key contributor to normal cochlear function.
- No evidence for electrogenic chloride secretion under cAMP control was found in Reissner's membrane.
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