Location and function of the epithelial Na channel in the cochlea

2001 ◽  
Vol 280 (2) ◽  
pp. F214-F222 ◽  
Author(s):  
Vincent Couloigner ◽  
Michel Fay ◽  
Sabri Djelidi ◽  
Nicolette Farman ◽  
Brigitte Escoubet ◽  
...  
Keyword(s):  
Stria Vascularis ◽  
Spiral Ganglion ◽  
Endocochlear Potential ◽  
Na Channel ◽  
Spiral Ligament ◽  
Α Subunit ◽  
Subunit Mrna ◽  
Spiral Limbus ◽  
Epithelial Na Channel

In the cochlea, endolymph is a K-rich and Na-poor fluid. The purpose of the present study was to check the presence and to assess the role of epithelial Na channel (ENaC) in this organ. α-, β-, and γ-ENaC subunit mRNA, and proteins were detected in rat cochlea by RT-PCR and Western blot. α-ENaC subunit mRNA was localized by in situ hybridization in both epithelial (stria vascularis, spiral prominence, spiral limbus) and nonepithelial structures (spiral ligament, spiral ganglion). The α-ENaC-positive tissues were also positive for β-subunit mRNA (except spiral ganglion) or for γ-subunit mRNA (spiral limbus, spiral ligament, and spiral ganglion), but the signals of β- and γ-subunits were weaker than those observed for α-subunit. In vivo, the endocochlear potential was recorded in guinea pigs under normoxic and hypoxic conditions after endolymphatic perfusion of ENaC inhibitors (amiloride, benzamil) dissolved either in K-rich or Na-rich solutions. ENaC inhibitors altered the endocochlear potential when Na-rich but not when K-rich solutions were perfused. In conclusion, ENaC subunits are expressed in epithelial and nonepithelial cochlear structures. One of its functions is probably to maintain the low concentration of Na in endolymph.

scholarly journals On the Interaction between Amiloride and Its Putative α-Subunit Epithelial Na+Channel Binding Site

2005 ◽  
Vol 280 (28) ◽  
pp. 26206-26215 ◽  
Author(s):  
Ossama B. Kashlan ◽  
Shaohu Sheng ◽  
Thomas R. Kleyman
Keyword(s):  
Binding Site ◽  
Na Channel ◽  
Α Subunit ◽  
Epithelial Na Channel

scholarly journals Feedback Inhibition of the epithelial Na+ channel (ENaC): in vitro vs. in vivo

2012 ◽  
Vol 26 (S1) ◽  
Author(s):  
Ankit Bharat Patel ◽  
Gustavo Frindt ◽  
Su Deng ◽  
Lawrence G. Palmer
Keyword(s):  
Feedback Inhibition ◽  
Na Channel ◽  
Epithelial Na Channel

scholarly journals Down-regulation of Na channel α-subunit mRNA by protein kinase C e in adrenal chromaffin cells

1997 ◽  
Vol 73 ◽  
pp. 157
Author(s):  
Toshihiko Yanagita ◽  
Hideyuki Kobayashi ◽  
Keizou Masumoto ◽  
Ryuichi Yamamoto ◽  
Tomoaki Yuhi ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Chromaffin Cells ◽  
Na Channel ◽  
Adrenal Chromaffin Cells ◽  
Down Regulation ◽  
Α Subunit ◽  
Subunit Mrna ◽  
Kinase C ◽  
Adrenal Chromaffin

Regulation of maturation and processing of ENaC subunits in the rat kidney

2006 ◽  
Vol 291 (3) ◽  
pp. F683-F693 ◽  
Author(s):  
Zuhal Ergonul ◽  
Gustavo Frindt ◽  
Lawrence G. Palmer
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Na Channel ◽  
Cortical Collecting Duct ◽  
Α Subunit ◽  
Salt Restriction ◽  
High K ◽  
Electrophysiological Measurements ◽  
Immature Form ◽  
Epithelial Na Channel

Antibodies directed against subunits of the epithelial Na channel (ENaC) were used together with electrophysiological measurements in the cortical collecting duct to investigate the processing of the proteins in rat kidney with changes in Na or K intake. When animals were maintained on a low-Na diet for 7–9 days, the abundance of two forms of the α-subunit, with apparent masses of 85 and 30 kDa, increased. Salt restriction also increased the abundance of the β-subunit and produced an endoglycosidase H (Endo H)-resistant pool of this subunit. The abundance of the 90-kDa form of the γ-subunit decreased, whereas that of a 70-kDa form increased and this peptide also exhibited Endo H-resistant glycosylation. These changes in α- and γ-subunits were correlated with increases in Na conductance elicited by a 4-h infusion with aldosterone. Changes in all three subunits were correlated with decreases in Na conductance when Na-deprived animals drank saline for 5 h. We conclude that ENaC subunits are mainly in an immature form in salt-replete rats. With Na depletion, the subunits mature in a process that involves proteolytic cleavage and further glycosylation. Similar changes occurred in α- and γ- but not β-subunits when animals were treated with exogenous aldosterone, and in β- and γ- but not α-subunits when animals were fed a high-K diet. Changes in the processing and maturation of the channels occur rapidly enough to be involved in the daily regulation of ENaC activity and Na reabsorption by the kidney.

Identification of a highly conserved sequence at the N-terminus of the epithelial Na + channel α subunit involved in gating

1999 ◽  
Vol 438 (5) ◽  
pp. 709-715 ◽  
Author(s):  
S. Gründer ◽  
N. Fowler Jaeger ◽  
I. Gautschi ◽  
L. Schild ◽  
B.C. Rossier
Keyword(s):  
Na Channel ◽  
Α Subunit ◽  
Conserved Sequence ◽  
N Terminus ◽  
Epithelial Na Channel

scholarly journals Induction of Redox-Active Gene Expression by CoCl2 Ameliorates Oxidative Stress-Mediated Injury of Murine Auditory Cells

Antioxidants ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 399 ◽  
Author(s):  
Jhang Ho Pak ◽  
Junyeong Yi ◽  
Sujin Ryu ◽  
In Ki Kim ◽  
Jung-Woong Kim ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Ganglion Cells ◽  
Stria Vascularis ◽  
Hypoxia Inducible Factor ◽  
Spiral Ganglion ◽  
Organ Of Corti ◽  
Luciferase Reporter ◽  
Related Factor ◽  
Redox Active

Free radicals formed in the inner ear in response to high-intensity noise, are regarded as detrimental factors for noise-induced hearing loss (NIHL). We reported previously that intraperitoneal injection of cobalt chloride attenuated the loss of sensory hair cells and NIHL in mice. The present study was designed to understand the preconditioning effect of CoCl2 on oxidative stress-mediated cytotoxicity. Treatment of auditory cells with CoCl2 promoted cell proliferation, with increases in the expressions of two redox-active transcription factors (hypoxia-inducible factor 1α, HIF-1α, nuclear factor erythroid 2-related factor 2; Nrf-2) and an antioxidant enzyme (peroxiredoxin 6, Prdx6). Hydrogen peroxide treatment resulted in the induction of cell death and reduction of these protein expressions, reversed by pretreatment with CoCl2. Knockdown of HIF-1α or Nrf-2 attenuated the preconditioning effect of CoCl2. Luciferase reporter analysis with a Prdx6 promoter revealed transactivation of Prdx6 expression by HIF-1α and Nrf-2. The intense immunoreactivities of HIF-1α, Nrf-2, and Prdx6 in the organ of Corti (OC), spiral ganglion cells (SGC), and stria vascularis (SV) of the cochlea in CoCl2-injected mice suggested CoCl2-induced activation of HIF-1α, Nrf-2, and Prdx6 in vivo. Therefore, we revealed that the protective effect of CoCl2 is achieved through distinctive signaling mechanisms involving HIF-1α, Nrf-2, and Prdx6.

scholarly journals The Epithelial Na+Channel Is Inhibited by a Peptide Derived from Proteolytic Processing of Its α Subunit

2006 ◽  
Vol 281 (27) ◽  
pp. 18901-18907 ◽  
Author(s):  
Marcelo D. Carattino ◽  
Shaohu Sheng ◽  
James B. Bruns ◽  
Joseph M. Pilewski ◽  
Rebecca P. Hughey ◽  
...  
Keyword(s):  
Proteolytic Processing ◽  
Na Channel ◽  
Α Subunit ◽  
Epithelial Na Channel

scholarly journals Ethanol Modulates the VR-1 Variant Amiloride-insensitive Salt Taste Receptor. I. Effect on TRC Volume and Na+ Flux

2005 ◽  
Vol 125 (6) ◽  
pp. 569-585 ◽  
Author(s):  
Vijay Lyall ◽  
Gerard L. Heck ◽  
Tam-Hao T. Phan ◽  
Shobha Mummalaneni ◽  
Shahbaz A. Malik ◽  
...  
Keyword(s):  
Taste Receptor ◽  
Na Channel ◽  
Mineral Salts ◽  
Tonic Component ◽  
Salt Taste ◽  
Vanilloid Receptor 1 ◽  
Intracellular Na Activity ◽  
Nerve Recordings ◽  
Epithelial Na Channel

The effect of ethanol on the amiloride- and benzamil (Bz)-insensitive salt taste receptor was investigated by the measurement of intracellular Na+ activity ([Na+]i) in polarized rat fungiform taste receptor cells (TRCs) using fluorescence imaging and by chorda tympani (CT) taste nerve recordings. CT responses were monitored during lingual stimulation with ethanol solutions containing NaCl or KCl. CT responses were recorded in the presence of Bz (a specific blocker of the epithelial Na+ channel [ENaC]) or the vanilloid receptor-1 (VR-1) antagonists capsazepine or SB-366791, which also block the Bz-insensitive salt taste receptor, a VR-1 variant. CT responses were recorded at 23°C or 42°C (a temperature at which the VR-1 variant salt taste receptor activity is maximally enhanced). In the absence of permeable cations, ethanol induced a transient decrease in TRC volume, and stimulating the tongue with ethanol solutions without added salt elicited only transient phasic CT responses that were insensitive to elevated temperature or SB-366791. Preshrinking TRCs in vivo with hypertonic mannitol (0.5 M) attenuated the magnitude of the phasic CT response, indicating that in the absence of mineral salts, transient phasic CT responses are related to the ethanol-induced osmotic shrinkage of TRCs. In the presence of mineral salts, ethanol increased the Bz-insensitive apical cation flux in TRCs without a change in cell volume, increased transepithelial electrical resistance across the tongue, and elicited CT responses that were similar to salt responses, consisting of both a transient phasic component and a sustained tonic component. Ethanol increased the Bz-insensitive NaCl CT response. This effect was further enhanced by elevating the temperature from 23°C to 42°C, and was blocked by SB-366791. We conclude that in the presence of mineral salts, ethanol modulates the Bz-insensitive VR-1 variant salt taste receptor.

Identification of a highly conserved sequence at the N-terminus of the epithelial Na+ channel α subunit involved in gating

1999 ◽  
Vol 438 (5) ◽  
pp. 709-715 ◽  
Author(s):  
S. Gründer ◽  
N. Fowler Jaeger ◽  
I. Gautschi ◽  
L. Schild ◽  
B.C. Rossier
Keyword(s):  
Na Channel ◽  
Α Subunit ◽  
Conserved Sequence ◽  
N Terminus ◽  
Epithelial Na Channel
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