The detailed localization pattern of Na+/K+/2Cl- cotransporter type 2 and its related ion transport system in the rat endolymphatic sac
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Updated: Jun 13, 2026

Study of the Functions and Activities of Neuronal K-Cl Co-Transporter KCC2 Using Western Blotting
Published on: December 9, 2022
Kosuke Akiyama1, Takenori Miyashita, Ai Matsubara
1Dept. of Otolaryngology, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan. kakaka@med.kagawa-u.ac.jp
Abstract:
The endolymphatic sac (ES) is a part of the membranous labyrinth. ES is believed to perform endolymph absorption, which is dependent on several ion transporters, including Na(+)/K(+)/2Cl(-) cotransporter type 2 (NKCC-2) and Na(+)/K(+)-ATPase. NKCC-2 is typically recognized as a kidney-specific ion transporter expressed in the apical membrane of the absorptive epithelium. NKCC-2 expression has been confirmed only in the rat and human ES other than the kidney, but the detailed localization features of NKCC-2 have not been investigated in the ES. Thus, we evaluated the specific site expressing NKCC-2 by immunohistochemical assessment. NKCC-2 expression was most frequently seen in the intermediate portion of the ES, where NKCC-2 is believed to play an important role in endolymph absorption. In addition, NKCC-2 expression was also observed on the apical membranes of ES epithelial cells, and Na(+)/K(+)-ATPase coexpression was observed on the basolateral membranes of ES epithelial cells. These results suggest that NKCC-2 performs an important role in endolymph absorption and that NKCC-2 in apical membranes and Na(+)/K(+)-ATPase in basolateral membranes work coordinately in the ES in a manner similar to that in renal tubules.
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