Localization of megalin in rat vestibular dark cells and endolymphatic sac epithelial cells.
CONCLUSIONS
Megalin immunoreactivity was observed in kidney proximal tubule cells, vestibular dark cells, and epithelial cells of the endolymphatic sac. Endocytic mechanisms appear to differ between the endolymphatic sac and proximal tubule cells. We speculate that megalin is secreted by a certain type of cell into the endolymphatic space, and is then absorbed from the endolymphatic space by another type of cell to maintain endolymphatic sac homeostasis.


OBJECTIVE
We previously detected megalin immunoreactivity in the rat cochlear duct. Megalin may be involved in endocytosis in the vestibular organ and endolymphatic sac. To examine this possibility, we extended our immunocytochemical investigation to the rat inner ear cells with special attention to vestibular dark cells and endolymphatic sac.


METHODS
We observed immunoreactivity of megalin under light and electron microscopy. The primary antibody was rabbit polyclonal antibody that had been raised against rat immunoaffinity-purified megalin.


RESULTS
The luminal membrane and subapical area of dark cells in the semicircular canal were immunolabeled. The stainable substance in the endolymphatic space was strongly stained. The cytoplasm of epithelial cells was also stained in various patterns.
Arai
Maki
M
Department of Otolaryngology, Hamamatsu University School of Medicine, Hamamatsu, Japan. maki-arai@hmedc.or.jp
Mizuta
Kunihiro
K
Saito
Akihiko
A
Hashimoto
Yasuyuki
Y
Iwasaki
Satoshi
S
Watanabe
Takahiro
T
Mineta
Hiroyuki
H
D000818:Animals; D003053:Cochlear Duct / Q000737:chemistry / Q000166:cytology; D004705:Endocytosis; D004712:Endolymphatic Sac / Q000737:chemistry / Q000166:cytology*; D004847:Epithelial Cells / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D007150:Immunohistochemistry; D007668:Kidney / Q000737:chemistry; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000032:analysis*; D008297:Male; D046529:Microscopy, Electron, Transmission; D051381:Rats; D017208:Rats, Wistar; D014722:Vestibule, Labyrinth / Q000737:chemistry / Q000166:cytology*
D026561:Low Density Lipoprotein Receptor-Related Protein-2