Institute of Experimental Animal Research, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan.
Acta Histochem Cytochem. 2009 Dec 29;42(6):159-69. doi: 10.1267/ahc.09023. Epub 2009 Nov 3.
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.
水通道蛋白是主要在细胞膜上水转运中起作用的膜水通道蛋白。在本研究中，我们通过免疫荧光、免疫过氧化物酶和免疫电镜研究了水通道蛋白 1（AQP1）、AQP3、AQP4 和 AQP5 在小鼠呼吸系统中的免疫组织化学分布。AQP3、AQP4 和 AQP5 表达于上皮细胞，而 AQP1 表达于上皮下结缔组织和毛细血管。在从鼻腔到肺内细支气管的气道表面上皮中，AQP5 主要定位于腔侧，AQP3 和 AQP4 定位于基底侧。在肺泡上皮中，AQP5 定位于Ⅰ型和Ⅱ型肺泡细胞的顶膜。与之前关于大鼠呼吸系统的研究相比，AQP5 局限于肺泡Ⅰ型细胞而不存在于气道表面上皮中，我们发现，在小鼠中 AQP5 分布更为广泛，遍及整个表面上皮。这些结果表明，AQP5 在水的处理中具有重要作用，例如维持气道表面液体和清除肺泡液。
