Hyposmotic stimulation-induced nitric oxide production in outer hair cells of the guinea pig cochlea.
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 Ca(2+)-free solution. L-N(G)-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 Ca(2+) concentrations ([Ca(2+)](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 Ca(2+) 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 [Ca(2+)](i) increase, which is presumably mediated by the activation of TRPV4 in OHCs. NO conversely inhibits the Ca(2+) response via the NO-cGMP-PKG pathway by a feedback mechanism.
Takeda-Nakazawa
Hiroko
H
Hearing Research Laboratory, Department of Otolaryngology, Kansai Medical University, Fumizonocho 10-15, Moriguchi, Osaka 570-8507, Japan.
Harada
Narinobu
N
Shen
Jing
J
Kubo
Nobuo
N
Zenner
Hans-Peter
HP
Yamashita
Toshio
T
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002227:Carbazoles / Q000494:pharmacology; D048429:Cell Size; D002478:Cells, Cultured; D003051:Cochlea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000378:metabolism; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000378:metabolism*; D007038:Hypotonic Solutions / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D008465:Mechanoreceptors / Q000187:drug effects / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D050916:TRPV Cation Channels / Q000819:agonists / Q000378:metabolism; D015854:Up-Regulation; D014882:Water-Electrolyte Balance / Q000187:drug effects
D002227:Carbazoles; D004791:Enzyme Inhibitors; D007038:Hypotonic Solutions; D007211:Indoles; D020030:Nitric Oxide Donors; D010703:Phorbol Esters; D047428:Protein Kinase Inhibitors; D050916:TRPV Cation Channels; C073601:KT 5823; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D005682:Gadolinium; D019001:Nitric Oxide Synthase; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; C038958:gadolinium chloride; D011188:Potassium; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester