Localization of aquaporins, water channel proteins, in the mouse eustachian tube.
CONCLUSIONS
Immunolocalization of the subtypes of water channel proteins, aquaporins (AQPs), was detected in the mouse eustachian tube (ET). AQPs are located continuously from the serous glands and the capillary vessels to the luminal side in the ET epithelium and may play an important role in the transportation of water to the surface of the ET lumen through the epithelium.


OBJECTIVE
Although the water supply to the surface of the ET lumen is considered to be essential for closing of the ET, the pathway of the water in the ET is not fully understood. Since AQPs, a group of water transport proteins, have been reported to regulate water homeostasis, we examined the location of AQPs in the mouse ET.


METHODS
Nine subtypes of AQPs were examined in paraffin embedded ETs of adult mice using the avidin-biotin peroxidase complex method of immunohistochemistry.


RESULTS
Four subtypes of AQPs were detected in the mouse ET. AQP-1 was detected in fibroblasts, endothelial cells of capillary vessels and cartilage cells. AQP-3 was distinctly detected in the basal membrane of epithelial cells. AQP-4 was detected in the basal membrane of epithelial cells. AQP-5 was expressed in the luminal side of the ET epithelial cells and also in the apical surface of the cells of the serous glands.
Takahashi
Etsu
E
Department of Otolaryngology & Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan. e-takahashi@orl.med.tohoku.ac.jp
Kikuchi
Toshihiko
T
Katori
Yukio
Y
Kobayashi
Toshimitsu
T
D000818:Animals; D020346:Aquaporins / Q000378:metabolism*; D002196:Capillaries / Q000166:cytology / Q000378:metabolism; D002356:Cartilage / Q000166:cytology / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism; D005064:Eustachian Tube / Q000166:cytology / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D008853:Microscopy
D020346:Aquaporins