Effects of nitric oxide on morphology of isolated cochlear outer hair cells: possible involvement in sensorineural hearing loss.
OBJECTIVE
One of the inflammatory mediators of otitis media, nitric oxide, can damage cochlear outer hair cells.


BACKGROUND
Free radicals, including nitric oxide, have been detected in middle ear effusion. Increasing evidence implicates free radicals in the pathogenesis of otitis media and possibly in the development of sensorineural hearing loss.


METHODS
Isolated outer hair cells from adult chinchilla cochlea were exposed to standard bathing solution (Control Group 1) or the nitric oxide-producing compounds, S-nitroso-N-acetyl, l-penicillamine (1-1.5 mg/ml, Experimental Group 1) or 3-morpholinosynonimine (1-1.5 mg/ml, Experimental Group 2). Since nitric oxide is readily converted to nitrite and nitrate in vivo, a second control group using sodium nitrite was used to separate potential effects of nitric oxide from nitrite (Control Group 2). All experiments were performed at an osmolality of 305 +/- 5 mOsm at room temperature, and with exposure time up to 90 minutes. The cells were observed using an inverted microscope, and the images were recorded and analyzed on the IMAGE Pro-Plus program.


RESULTS
Outer hair cells exposed to either standard bathing solution or sodium nitrite (Control Groups 1 and 2) showed no significant change in cell shape or length. Cells exposed to S-nitroso-N-acetyl and l-penicillamine or 3-morpholinosynonimine exhibited ballooning and significant shortening in mean cell length (p < 0.01).


CONCLUSIONS
This study demonstrates that exposure to nitric oxide causes irreversible morphologic changes in isolated outer hair cells, suggesting possible involvement of nitric oxide radical in the development of sensorineural hearing loss as a sequela of chronic otitis media.
Jung
Timothy T K
TT
Division of Otolaryngology-Head and Neck Surgery, Loma Linda University School of Medicine, and Jerry L. Pettis Memorial Veterans Medical Center, Loma Linda, California, USA. tjung1790@aol.com
Llaurado
Raymund J
RJ
Nam
Boo Hyun
BH
Park
Seong Kook
SK
Kim
Paul D
PD
John
Earnest O
EO
D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000648:ultrastructure; D048429:Cell Size / Q000187:drug effects; D002682:Chinchilla; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000473:pathology*; D006319:Hearing Loss, Sensorineural / Q000209:etiology; D018836:Inflammation Mediators / Q000502:physiology; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology
D018836:Inflammation Mediators; D020030:Nitric Oxide Donors; D009569:Nitric Oxide; C002385:linsidomine; D026423:S-Nitroso-N-Acetylpenicillamine; D008981:Molsidomine