Effects of alpha-tocopherol on noise-induced hearing loss in guinea pigs.
Preventing noise-induced hearing loss (NIHL) by antioxidants is based on the hypothesis that generation of reactive oxygen species is one of the causes of NIHL. alpha-Tocopherol is a naturally occurring antioxidant with no noticeable side effects. In this study, we attempted to protect guinea pigs from developing NIHL by administering alpha-tocopherol. Pigmented male guinea pigs were exposed to a noise (4 kHz octave band, 100 dB SPL), 8 h/day for 3 days consecutively. alpha-Tocopherol (10 mg/kg or 50 mg/kg daily) was given by intraperitoneal injection from 3 days before through 3 days after the noise exposure. Auditory evoked brainstem response (ABR) thresholds at 2, 4 and 8 kHz were recorded prior to the experiment, immediately post-noise, 2 and 8 days post-noise. On day 8 post-noise, after the ABR recording, guinea pigs were decapitated and the cochleae were removed for cochlear surface preparations and scanning electron microscope (SEM) study. ABR threshold shifts of groups receiving alpha-tocopherol were significantly smaller than those of groups not receiving alpha-tocopherol at all frequencies and all time points tested except that of group 3 at 8 kHz 8 days post-noise. No hair cell loss was seen on the surface preparations, but stereocilia loss was found by SEM study. The noise-induced stereocilia loss was significantly decreased by alpha-tocopherol. These results indicate that alpha-tocopherol can attenuate the noise-induced cochlear damage. Further investigations on the preventive effect of alpha-tocopherol on NIHL in noise-exposed workers are necessary.
Hou
Fenxia
F
Department of Occupational Health, School of Public Health, Health Science Center, Peking University, Beijing, PR China. houfenxia@yahoo.com.cn
Wang
Sheng
S
Zhai
Suoqiang
S
Hu
Yinyan
Y
Yang
Weiyan
W
He
Lihua
L
D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology*; D002923:Cilia / Q000187:drug effects / Q000648:ultrastructure; D003051:Cochlea / Q000187:drug effects / Q000648:ultrastructure; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000648:ultrastructure; D006317:Hearing Loss, Noise-Induced / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D007274:Injections, Intraperitoneal; D008297:Male; D008855:Microscopy, Electron, Scanning; D024502:alpha-Tocopherol / Q000008:administration & dosage / Q000494:pharmacology*
D000975:Antioxidants; D024502:alpha-Tocopherol