Expression and immunolocalization of aquaporin-6 (Aqp6) in the rat inner ear.
CONCLUSIONS
Since aquaporin-6 (Aqp6) protein was located in the membrane of intracellular vesicles of the stria vascularis, endolymphatic sac, and vestibule, Aqp6 might be involved in some distinct physiological function of acid-base metabolism and water balance in endolymphatic fluid homeostasis. However, its lack of expression on the plasma membrane indicates that Aqp6 does not have a direct role in water flux via the plasma membrane.


OBJECTIVE
To evaluate the expression and immunolocalization of Aqp6 in the rat inner ear.


METHODS
Wistar rats were used. Aqp6 mRNA expression in the rat inner ear was investigated in the vestibulum as well as in the cochlea and endolymphatic sac using the reverse transcription-polymerase chain reaction (RT-PCR) method, and detailed immunolocalization of Aqp6 in the rat inner ear was investigated using immunohistochemical methods including immunofluorescence microscopy and immunoelectron microscopy.


RESULTS
We obtained novel data showing that not just Aqp6 mRNA but also Aqp6 protein is expressed in the cochlea, endolymphatic sac, and vestibule. Immunoelectron microscopic studies revealed that the immunolabelled gold was diffusely seen in the intracellular area of the stria vascularis, endolymphatic sac, and vestibule, but never in the plasma membranes.
Taguchi
Daizo
D
Department of Otolaryngology, Kochi Medical School, Kochi, Japan. taguchident@aol.com
Takeda
Taizo
T
Kakigi
Akinobu
A
Okada
Teruhiko
T
Nishioka
Rie
R
Kitano
Hiroya
H
D000818:Animals; D051403:Aquaporin 6 / Q000235:genetics / Q000378:metabolism*; D003051:Cochlea / Q000378:metabolism* / Q000648:ultrastructure; D004710:Endolymph; D005260:Female; D016253:Microscopy, Immunoelectron; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014722:Vestibule, Labyrinth / Q000378:metabolism* / Q000648:ultrastructure
D051403:Aquaporin 6; D012333:RNA, Messenger