Ascorbic acid reduces noise-induced nitric oxide production in the guinea pig ear.
OBJECTIVE
Noise-induced hearing loss can be caused, among other causes, by increased nitric oxide (NO) production in the inner ear leading to nitroactive stress and cell destruction. Some studies in the literature suggest that the degree of hearing loss (HL) could be reduced in an animal model through ascorbic acid supplementation. To identify the effect of ascorbic acid on tissue-dependent NO content in the inner ear of the guinea pig, we determined the local NO production in the organ of Corti and the lateral wall separately 6 hours after noise exposure.


METHODS
Prospective animal study in guinea pigs.


METHODS
Over a period of 7 days, male guinea pigs were supplied with minimum (25 mg/kg body weight/day) and maximum (525 mg/kg body weight/day) ascorbic acid doses, and afterwards exposed to noise (90 dB sound pressure level for 1 hour). The acoustic-evoked potentials were recorded before and after noise exposure. The organ of Corti and the lateral wall were incubated differently for 6 hours in culture medium, and the degree of NO production was determined by chemiluminescence.


RESULTS
Ascorbic acid treatment reduced the hearing threshold shift after noise exposure depending on concentration. When the maximum ascorbic acid dose was substituted, NO production was significantly reduced in the lateral wall after noise exposure and slightly reduced in the organ of Corti.


CONCLUSIONS
Oral supplementation of the natural radical scavenger ascorbic acid reduces the NO-production rate in the inner ear in noisy conditions. This finding supports the concept of inner ear protection by ascorbic acid supplementation.
Heinrich
Ulf-Rüdiger
UR
Department of Otorhinolaryngology, Johannes Gutenberg University Medical School Mainz, Mainz, Germany. heinrich@hno.klinik.uni-mainz.de
Fischer
Ilka
I
Brieger
Jürgen
J
Rümelin
Andreas
A
Schmidtmann
Irene
I
Li
Huige
H
Mann
Wolf J
WJ
Helling
Kai
K
D000818:Animals; D001205:Ascorbic Acid / Q000097:blood / Q000494:pharmacology*; D003051:Cochlea / Q000378:metabolism; D007758:Ear, Inner / Q000378:metabolism*; D005072:Evoked Potentials, Auditory; D006168:Guinea Pigs; D008297:Male; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D009622:Noise / Q000009:adverse effects*; D009925:Organ of Corti / Q000378:metabolism; D011446:Prospective Studies; D011897:Random Allocation
D009569:Nitric Oxide; D001205:Ascorbic Acid