NKCCs in the fibrocytes of the spiral ligament are silent on the unidirectional K+ transport that controls the electrochemical properties in the mammalian cochlea

Takamasa Yoshida, Fumiaki Nin, Genki Ogata, Satoru Uetsuka, Tadashi Kitahara, Hidenori Inohara, Kohei Akazawa, Shizuo Komune, Yoshihisa Kurachi, Hiroshi Hibino

Research output: Contribution to journalArticle

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Abstract

Unidirectional K+ transport across the lateral cochlear wall contributes to the endocochlear potential (EP) of +80 mV in the endolymph, a property essential for hearing. The wall comprises two epithelial layers, the syncytium and the marginal cells. The basolateral surface of the former and the apical membranes of the latter face the perilymph and the endolymph, respectively. Intrastrial space (IS), an extracellular compartment between the two layers, exhibits low [K+] and a potential similar to the EP. This IS potential (ISP) dominates the EP and represents a K+ diffusion potential elicited by a large K+ gradient across the syncytial apical surface. The K+ gradient depends on the unidirectional K+ transport driven by Na+,K+-ATPases on the basolateral surface of each layer and the concomitant Na+,K+,2Cl-cotransporters (NKCCs) in the marginal cell layer. The NKCCs coexpressed with the Na+,K+-ATPases in the syncytial layer also seem to participate in the K+ transport. To test this hypothesis, we examined the electrochemical properties of the lateral wall with electrodes measuring [K+] and potential. Blocking NKCCs by perilymphatic perfusion of bumetanide suppressed the ISP. Unexpectedly and unlike the inhibition of the syncytial Na+,K+-ATPases, the perfusion barely altered the electrochemical properties of the syncytium but markedly augmented [K+] of the IS. Consequently, the K+ gradient decreased and the ISP declined. These observations resembled those when the marginal cells’ Na+,K+-ATPases or NKCCs were blocked with vascularly applied inhibitors. It is plausible that NKCCs in the marginal cells are affected by the perilymphatically perfused bumetanide, and these transporters, but not those in the syncytium, mediate the unidirectional K+ transport.

Original languageEnglish
Pages (from-to)1577-1589
Number of pages13
JournalPflugers Archiv European Journal of Physiology
Volume467
Issue number7
DOIs
Publication statusPublished - Jul 13 2015

Fingerprint

Spiral Ligament of Cochlea
Ligaments
Cochlea
Electrochemical properties
Adenosine Triphosphatases
Giant Cells
Endolymph
Bumetanide
Perfusion
Perilymph
Extracellular Space
Audition
Hearing
Electrodes
Cells
Membranes
sodium-translocating ATPase

All Science Journal Classification (ASJC) codes

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

Cite this

NKCCs in the fibrocytes of the spiral ligament are silent on the unidirectional K+ transport that controls the electrochemical properties in the mammalian cochlea. / Yoshida, Takamasa; Nin, Fumiaki; Ogata, Genki; Uetsuka, Satoru; Kitahara, Tadashi; Inohara, Hidenori; Akazawa, Kohei; Komune, Shizuo; Kurachi, Yoshihisa; Hibino, Hiroshi.

In: Pflugers Archiv European Journal of Physiology, Vol. 467, No. 7, 13.07.2015, p. 1577-1589.

Research output: Contribution to journalArticle

Yoshida, Takamasa ; Nin, Fumiaki ; Ogata, Genki ; Uetsuka, Satoru ; Kitahara, Tadashi ; Inohara, Hidenori ; Akazawa, Kohei ; Komune, Shizuo ; Kurachi, Yoshihisa ; Hibino, Hiroshi. / NKCCs in the fibrocytes of the spiral ligament are silent on the unidirectional K+ transport that controls the electrochemical properties in the mammalian cochlea. In: Pflugers Archiv European Journal of Physiology. 2015 ; Vol. 467, No. 7. pp. 1577-1589.
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AU - Uetsuka, Satoru

AU - Kitahara, Tadashi

AU - Inohara, Hidenori

AU - Akazawa, Kohei

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