INFLUENCE OF INTENSE SOUND EXPOSURE ON GLUTATHIONE SYNTHESIS IN THE COCHLEA

Previous studies have shown that depletion of endogenous glutathione ( GSH) potentiates noise-induced hearing loss (NIHL), whereas replenishm ent of GSH attenuates NIHL (Yamasoba et al., Brain Res. 784 (1998) 82- 90). Since these findings indicate an important role of GSH in protect ion from NIHL, we assessed the influence of intense sound exposure (br oadband noise, 105 dB SPL, 5 h) on GSH and cysteine levels in the guin ea pig cochlea using high performance liquid chromatography. GSH level s were significantly increased in the lateral wall 2 and 4 h post-expo sure and returned to normal 6 h post-exposure. GSH levels in the senso ry epithelium and modiolus did not show significant changes following noise. Cysteine levels were unchanged in any of the cochlear segments. For the cochlea as a whole, intense sound exposure did not significan tly change GSH or cysteine levels throughout the 6-h measurement perio d post-exposure. These results indicate that GSH synthesis is markedly upregulated selectively in the lateral wall by noise exposure, presum ably in response to the robust consumption of GSH, as it is utilized i n scavenging reactive oxygen species. (C) 1998 Elsevier Science B.V. A ll rights reserved.