title: Selective expression of aquaporin 1, 4 and 5 in the rat middle ear.
abstract: The middle ear cavity is an air-filled space that must be maintained for effective sound transmission to the inner ear. To examine the mechanisms of water homeostasis in the middle ear, we investigated whether aquaporins (AQPs), a family of water-permeable channels, were expressed in the middle ear. Reverse transcription-polymerase chain reaction and immunoblot analyses revealed that mRNAs encoding AQP1, 4 and 5 (but not 2 or 3) subtypes were expressed in rat middle ear epithelium; AQP1, 4 and 5 were detected as 28-, 30- and 30-kDa proteins, respectively. Immunohistochemical analysis showed that AQP1 was localized at capillary endothelial cells and fibroblasts in lamina propria mucosae; AQP4 was present solely at the basolateral membrane of ciliated cells, whereas AQP5 was on the apical surface of ciliated cells as well as of flat and columnar epithelial cells. The characteristic different localizations of AQP1, 4 and 5 subtypes in the middle ear suggest that middle ear water homeostasis requires the coordinated operation of these AQPs.
authors.affiliation: Department of Pharmacology, Miyazaki Medical College, Kiyotake, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Minami
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.forename: A
authors.initials: A
authors.lastname: Yamashita
authors.forename: T
authors.initials: T
authors.lastname: Yanagita
authors.forename: Y
authors.initials: Y
authors.lastname: Uezono
authors.forename: H
authors.initials: H
authors.lastname: Yokoo
authors.forename: S
authors.initials: S
authors.lastname: Shiraishi
authors.forename: T
authors.initials: T
authors.lastname: Saitoh
authors.forename: Y
authors.initials: Y
authors.lastname: Asada
authors.forename: S
authors.initials: S
authors.lastname: Komune
authors.forename: A
authors.initials: A
authors.lastname: Wada
mesh_terms: D000818:Animals; D051398:Aquaporin 1; D051401:Aquaporin 4; D051402:Aquaporin 5; D020346:Aquaporins / Q000378:metabolism*; D004432:Ear, Middle / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: C496022:Aqp1 protein, rat; C496032:Aqp4 protein, rat; C496040:Aqp5 protein, rat; D051401:Aquaporin 4; D051402:Aquaporin 5; D020346:Aquaporins; D008565:Membrane Proteins; D051398:Aquaporin 1