Expression of water channel proteins (aquaporins) in the rat Eustachian tube and middle ear mucosa.
CONCLUSIONS
Diverse expression of the different subtypes of aquaporins in different parts of the Eustachian tube and middle ear suggests region-specific functions of the aquaporins in the normal physiology of the tubotympanum and also suggests that they may play roles in the pathophysiology of otitis media.


OBJECTIVE
The epithelial cells of the middle ear and Eustachian tube must maintain adequate water balance for normal function of the mucociliary system. Since aquaporins (AQPs) are known to play critical roles in water homeostasis, we investigated their expression in the tubotympanum of the rat.


METHODS
The expression of AQP subtypes 1, 2, 4, 5, and 7 were examined in the rat Eustachian tube and middle ear using RT-PCR, Western blotting, and immunohistochemistry.


RESULTS
Transcripts for AQP 1, 4, and 5 were detected in the Eustachian tube and middle ear. Expression of these molecules at the protein level was confirmed by Western blot analysis. Immunohistochemical analysis demonstrated that AQP 4 was localized to the basolateral membranes of ciliated epithelial cells while AQP 5 was localized to the apical surface of serous gland cells, but not goblet cells, in the rat Eustachian tube. AQP 1 was found to be expressed by the subepithelial fibroblasts.
Kang
Sung-Ho
SH
Gonda Department of Cell and Molecular Biology, House Ear Institute, Los Angeles, CA 90057, USA.
Chang
Ki-Hong
KH
Ohcho
Shuji
S
Lee
Haa-Yung
HY
Cha
Kiweon
K
Moon
Sung-Kyun
SK
Andalibi
Ali
A
Lim
David J
DJ
D000818:Animals; D020346:Aquaporins / Q000378:metabolism*; D001485:Basement Membrane / Q000378:metabolism; D015153:Blotting, Western; D004432:Ear, Middle / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D005064:Eustachian Tube / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D007150:Immunohistochemistry; D009092:Mucous Membrane / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D020133:Reverse Transcriptase Polymerase Chain Reaction
D020346:Aquaporins; D012333:RNA, Messenger