The Study of Distribution and Expression of Water Channel Proteins(Aquaporins) in the Rat Eustachian Tube / 대한이비인후과학회지

ABSTRACT

BACKGROUND AND OBJECTIVES: The mucosal epithelium of middle ear and eustachian tube needs hydration to maintain proper amount of moisture. Recent discoveries of various types of water channel proteins (aquaporins ; AQPs) in mucous epithelium suggest that they play critical roles in the regional regulation of water balance. The purpose of this study is to assess the distribution and expression of different subtypes of AQPs in the rat eustachian tube. SUBJECTS AND METHOD: We analyzed the distribution and expression of AQP1, 2, 4, 5, and 7 using RT-PCR, Western blot, and immunohistochemistry study in the rat middle ear and eustachian tube samples. RESULTS: The expression of the mRNA of AQP1, 4, and 5 were observed in the rat eustachian tube and middle ear. The bands of AQP1, 4, and 5 were detected at 28 kDa, 31 kDa, and 26 kDa proteins in the Western blot analysis, respectively. The immunohistochemical analysis demonstrated that AQP1 was expressed in fibroblasts at subepithelial portions of the rat eustachian tube and that AQP4 was observed at the basolateral membrane of the ciliated epithelial cells. The distribution of AQP5 in rat eustachian tube was limited to the apical surface of serous gland cells, but all of the epithelial goblet cells were labeled negative. CONCLUSION: We demonstrated that there are various subtypes of AQP in rat eustachian tube and that they existed at specific cells and sites. This study may be a preliminary study to determine the possibility of relationship between AQP expression and AQP-related disease in the middle ear and eustachian tube.