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Isolation and Culture of Primary Marginal Cells of the Stria Vascularis from Neonatal Mice
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Ca(2+) regulation of endocochlear potential in marginal cells
Yoshiaki Mori1, Masahito Watanabe, Takaki Inui
1Department of Physiology II, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, Osaka, 569-8686, Japan.
The Journal of Physiological Sciences : JPS
|June 9, 2009
Summary
Cytosolic calcium in cochlear marginal cells regulates the positive endocochlear potential (EP). Inhibiting calcium channels or pumps affects EP during asphyxia and furosemide exposure, impacting hearing function.
Area of Science:
- Otolaryngology
- Cell Physiology
- Neuroscience
Background:
- The endocochlear potential (EP) is crucial for hearing.
- Marginal cells in the cochlea play a key role in maintaining EP.
- Cytosolic calcium concentration ([Ca2+]c) in these cells is implicated in EP regulation.
Purpose of the Study:
- To investigate the role of cytosolic calcium in marginal cells on EP changes induced by asphyxia or furosemide.
- To identify the specific calcium channels and pumps involved in EP regulation.
Main Methods:
- Perfusion of cochlear endolymph with calcium chelators (EGTA-AM) or channel/pump inhibitors (SKF96365, nifedipine, thapsigargin).
- Induction of EP changes via transient asphyxia or intravenous furosemide administration.
- Immunohistochemical staining for TRPC and epithelial sodium channels.
Main Results:
- SKF96365 and EGTA-AM inhibited EP decreases during both asphyxia and furosemide treatment.
- Nifedipine inhibited asphyxia-induced EP decrease but not furosemide-induced decrease.
- Thapsigargin inhibited EP decreases during both conditions, suggesting a role for the endoplasmic Ca2+-pump.
- TRPC channels and epithelial Na+ channels were localized in marginal cell membranes.
- Amiloride and phenamil reduced the positive EP.
Conclusions:
- Cytosolic calcium, regulated by endoplasmic Ca2+-pump and Ca2+-permeable channels in marginal cells, is vital for maintaining the positive EP.
- The EP is partly generated by a sodium diffusion potential across the marginal cell basolateral membrane.
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