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How can teleostean inner ear hair cells maintain the proper association with the accreting otolith?
Author(s) -
Shiao JenChieh,
Lin LiYih,
Horng JiunLin,
Hwang PungPung,
Kaneko Toyoji
Publication year - 2005
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.20578
Subject(s) - biology , otolith , inner ear , association (psychology) , anatomy , fish <actinopterygii> , fishery , philosophy , epistemology
The perception of equilibrium and sound in fish depends on the deflection of hair bundles of hair cell by the otolith. However, the accreting nature of teleostean otoliths poses a problem for maintenance of proper contact between the hair bundle and the otolith surface. Immunocytochemical staining localizes abundant proton‐secreting H + ‐ATPase in the apical membrane of the hair cells. The H + ‐ATPase‐mediated proton secretion into the endolymph causes an approximately 0.4‐unit pH decrease, which was quantified by an H + ‐selective microelectrode. Thus, the hair cells maintain the proper distance from the otolith by neutralizing the alkaline endolymph to retard CaCO 3 deposition on the otolith opposite the sensory macula. Carbonic anhydrase, which hydrolyses CO 2 and produces HCO 3 – and H + , was also localized in the hair cells. Ionocytes showed prominent immunostaining of carbonic anhydrase and Na + ‐K + ‐ATPase, indicating its role in transepithelial transport of HCO 3 – across the membranous labyrinth into the endolymph. Ionocytes form a ring closely surrounding the sensory macula. HCO 3 – secreted from the ionocytes may serve as a barrier to neutralize H + diffused from the sensory macula while keeping the endolymph alkaline outside the sensory macula. The ingenious arrangement of ionocytes and hair cells results in a unique sculptured groove, which is a common feature on the proximal surface of all teleostean otoliths. J. Comp. Neurol. 488:331–341, 2005. © 2005 Wiley‐Liss, Inc.