Effect of superoxide dismutase and allopurinol on impulse noise-exposed guinea pigs--electrophysiological and biochemical study.
OBJECTIVE
To investigate the protective effect of two anti-reactive oxygen species (ROS) substances, copper-zinc superoxide dismutase (CuZn-SOD) and allopurinol, in impulse noise-exposed guinea pigs.


METHODS
Allopurinol or CuZn-SOD were administered intraperitoneally before exposure to 125 dB SPL noise centered at 2.0-3.0 kHz, with a repetition rate of 4/s, for 1.8 h. Hearing thresholds were tested by means of electrocochleography after implanting the animals with permanent electrodes. The presence of lipoperoxides in the guinea pig cochleae exposed to noise-induced oxidative stress was determined by means of the dosage of malondialdhyde, evaluated by measuring the content of thiobarbituric acid reactive substances in perilymph samples.


RESULTS
Acoustic stress induced ROS formation and both allopurinol and CuZn-SOD exerted a protective effect on the cochlea. Comparison of compound action potential thresholds in different animal groups showed that the temporary threshold shift was significantly lower in treated animals than in those without pharmacological protection.


CONCLUSIONS
The protective effect of the antioxidant agents demonstrates that, even at a high level of impulse noise exposure, a metabolic mechanism of cochlear damage may still play an important role in noise-exposed sensorineural hearing loss.
Department of Experimental and Clinical Medicine, University of Reggio, Reggio, Italy.
E
E
Cassandro
L
L
Sequino
P
P
Mondola
G
G
Attanasio
M
M
Barbara
R
R
Filipo
D000493:Allopurinol / Q000494:pharmacology*; D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects*; D003051:Cochlea / Q000293:injuries / Q000378:metabolism*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects*; D016166:Free Radical Scavengers / Q000494:pharmacology*; D006168:Guinea Pigs; D006317:Hearing Loss, Noise-Induced / Q000378:metabolism / Q000517:prevention & control*; D008054:Lipid Peroxides / Q000032:analysis; D008315:Malondialdehyde / Q000032:analysis; D009622:Noise / Q000009:adverse effects*; D018384:Oxidative Stress; D010498:Perilymph / Q000737:chemistry; D013482:Superoxide Dismutase / Q000494:pharmacology*; D013858:Thiobarbiturates / Q000032:analysis
D016166:Free Radical Scavengers; D008054:Lipid Peroxides; D013858:Thiobarbiturates; D008315:Malondialdehyde; D000493:Allopurinol; D013482:Superoxide Dismutase; C029684:thiobarbituric acid