Immunohistochemical localization of the aquaporins AQP1
 AQP3
 AQP4
 and AQP5 in the mouse respiratory system

Toshiyuki Matsuzaki
Hidekazu Hata
Hitoshi Ozawa
Kuniaki Takata

Aquaporins are membrane water channel proteins that function mainly in water transfer across cellular membranes. In our present study
 we investigated the immunohistochemical distribution of aquaporin 1 (AQP1)
 AQP3
 AQP4
 and AQP5 in the mouse respiratory system by immunofluorescence
 immunoperoxidase
 and immunoelectron microscopy. AQP3
 AQP4
 and AQP5 are expressed in epithelial cells
 whereas AQP1 is expressed in subepithelial connective tissues and capillaries. In the airway surface epithelia from the nasal cavity to the intrapulmonary bronchioles
 AQP5 was found to be mainly localized to the luminal side and both AQP3 and AQP4 to the abluminal side. In the alveolar epithelium
 AQP5 is localized to the apical membranes of both type I and type II alveolar cells. Compared with the previous studies on the rat respiratory system
 in which AQP5 is restricted to the alveolar type I cells and absent from the airway surface epithelia
 we found that AQP5 in the mouse is much more widely distributed throughout the surface epithelia. These results suggest that AQP5 has a critical role in water-handling
 such as the maintenance of airway surface liquid and clearance of alveolar fluid in the mouse respiratory system. c 2009 The Japan Society of Histochemistry and Cytochemistry.

Acta Histochemica et Cytochemica

42

6

10.1267/ahc.09023

https://doi.org/10.1267/ahc.09023