Introduction:
Intense noise exposure results in increased nitric oxide (NO)-production by inducible NO-Synthase (iNOS) overexpression. It is unclear, whether the constitutively expressed endothelial nitric oxide synthase (eNOS) may act in an otoprotective manner after noise exposure of the cochlea.
Methods:
Eleven male guinea pigs were exposed to 90 dB SPL for 1 hour (h) and 2 animals for 2h, with 5 or 6 animals serving as controls, respectively. On paraffin sections eNOS immunostaining was analyzed and quantified after noise (1h) in 4 cochlear regions by light microscopy. After 2h noise exposure, an eNOS-specific gold-labeling was quantified on sections of the Organ of Corti at the electron microscopic level.
Results:
The expression of the eNOS isoform in the guinea pig cochlea was found to be already up-regulated 1h after noise exposure in all 4 cochlear regions. At the ultrastructural level, a clear increase of the eNOS expression was located in actin-containing cells linked to the reticular lamina of the Organ of Corti 2h after noise exposure.
Conclusion:
Distinct alterations in of eNOS expression patterns may indicate an early intrinsic otoprotective mechanism of the inner ear after noise exposure.
