Expressions of aquaporin-2, vasopressin type 2 receptor, transient receptor potential channel vanilloid (TRPV)1, and TRPV4 in the human endolymphatic sac.
OBJECTIVE
To localize aquaporin (AQP)2, vasopressin type 2 receptor (V2-R), and transient receptor potential channel vanilloid subfamily 1, 4 (TRPV1, TRPV4) in the human endolymphatic sac (ES).


METHODS
Three samples of human ES were sampled during the removal of vestibular schwannoma by way of the translabyrinthine approach. The samples were immediately fixed in 4% paraformaldehyde and embedded in OCT compound; immunohistochemistry was performed with AQP2, V2-R, TRPV1, and TRPV4 polyclonal antibodies.


RESULTS
AQP2, V2-R, TRPV1, and TRPV4 proteins were detected in the epithelial layer of the ES but were not observed in connective tissue around the ES. TRPV1 was also expressed in blood vascular endothelial cells of the connective tissue of ES.


CONCLUSIONS
AQP2, V2-R, and TRPV4 were expressed in the luminal epithelium of human ES. The same characteristic distribution of water and ion channels is seen in the kidney, where a significant amount of fluid is filtrated and resorbed. ES probably plays an active role in the homeostasis of the endolymph.
Taguchi
Daizo
D
Department of Otolaryngology, Kochi Medical School, Nankoku, Kochi, Japan. jm-taguchid@kochi-u.ac.jp
Takeda
Taizo
T
Kakigi
Akinobu
A
Takumida
Masaya
M
Nishioka
Rie
R
Kitano
Hiroya
H
D000906:Antibodies / Q000276:immunology; D051399:Aquaporin 2 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D004712:Endolymphatic Sac / Q000276:immunology / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D009464:Neuroma, Acoustic / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D009997:Osmotic Pressure; D017483:Receptors, Vasopressin / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*
C496023:AQP2 protein, human; D000906:Antibodies; D051399:Aquaporin 2; D017483:Receptors, Vasopressin; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; C416986:TRPV4 protein, human