Abstract
Nitric oxide (NO) production during hyposmotic stimulation in outer hair cells (OHCs) of the guinea pig cochlea was investigated using the NO sensitive dye DAF-2. Simultaneous measurement of the cell length and NO production showed rapid hyposmotic-induced cell swelling to precede NO production in OHCs. Hyposmotic stimulation failed to induce NO production in the Ca2+-free solution. L-NG-nitroarginine methyl ester (L-NAME), a non-specific NO synthase inhibitor and gadolinium, a stretch-activated channel blocker inhibited the hyposmotic stimulation-induced NO production whereas suramin, a P2 receptor antagonist did not. S-nitroso-N-acetylpenicillamine (SNAP), a NO donor inhibited the hyposmotic stimulation-induced increase in the intracellular Ca2+ concentrations ([Ca2+]i) while L-NAME enhanced it. 1H-[1,2,4]oxadiazole[4,3a]quinoxalin-1-one, an inhibitor of guanylate cyclase and KT5823, an inhibitor of cGMP-dependent protein kinase (PKG) mimicked effects of L-NAME on the Ca2+ response. Transient receptor potential vanilloid 4 (TRPV4), an osmo- and mechanosensitive channel was expressed in the OHCs by means of immunohistochemistry. 4alpha-phorbol 12,13-didecanoate, a TRPV4 synthetic activator, induced NO production in OHCs. These results suggest that hyposmotic stimulation can induce NO production by the [Ca2+]i increase, which is presumably mediated by the activation of TRPV4 in OHCs. NO conversely inhibits the Ca2+ response via the NO-cGMP-PKG pathway by a feedback mechanism.
Publication types
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Corrected and Republished Article
MeSH terms
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8-Bromo Cyclic Adenosine Monophosphate / pharmacology
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Animals
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Calcium / metabolism
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Carbazoles / pharmacology
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Cell Size* / drug effects
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Cells, Cultured
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Cyclic GMP / metabolism
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Cyclic GMP-Dependent Protein Kinases / antagonists & inhibitors
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Cyclic GMP-Dependent Protein Kinases / metabolism
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Enzyme Inhibitors / pharmacology
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Gadolinium / pharmacology
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Guanylate Cyclase / antagonists & inhibitors
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Guanylate Cyclase / metabolism
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Guinea Pigs
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Hair Cells, Auditory, Outer / drug effects
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Hair Cells, Auditory, Outer / metabolism*
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Hypotonic Solutions
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Indoles / pharmacology
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Kinetics
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Membrane Potentials
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NG-Nitroarginine Methyl Ester / pharmacology
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Nitric Oxide / metabolism*
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Nitric Oxide Donors / pharmacology
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Nitric Oxide Synthase / antagonists & inhibitors
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Nitric Oxide Synthase / metabolism
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Organ of Corti / cytology
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Organ of Corti / drug effects
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Organ of Corti / metabolism*
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Osmotic Pressure
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Phorbol Esters / pharmacology
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Potassium / metabolism
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Purinergic P2 Receptor Antagonists
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Receptors, Purinergic P2 / metabolism
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S-Nitroso-N-Acetylpenicillamine / pharmacology
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Signal Transduction* / drug effects
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Sodium Chloride / metabolism
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Suramin / pharmacology
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TRPV Cation Channels / agonists
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TRPV Cation Channels / metabolism
Substances
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Carbazoles
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Enzyme Inhibitors
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Hypotonic Solutions
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Indoles
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Nitric Oxide Donors
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Phorbol Esters
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Purinergic P2 Receptor Antagonists
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Receptors, Purinergic P2
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TRPV Cation Channels
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KT 5823
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8-Bromo Cyclic Adenosine Monophosphate
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Nitric Oxide
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Sodium Chloride
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Suramin
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S-Nitroso-N-Acetylpenicillamine
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Gadolinium
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Nitric Oxide Synthase
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Cyclic GMP-Dependent Protein Kinases
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Guanylate Cyclase
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Cyclic GMP
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gadolinium chloride
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Potassium
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Calcium
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NG-Nitroarginine Methyl Ester