Cochlear expression patterns of endothelial nitric oxide synthase in guinea pigs after loud noiseDeutsche Forschungsgemeinschaft (DFG grant STR 1014); Impulsfonds des Landes Rheinland-Pfalz 2017 – 2018 (Research Initiative of the Government of Rhineland-Palatia); BiomaTiCS-Programm der Universitätsmedizin Mainz, ('Biomaterials, Tissues and Cells'-program, University Medical Center Mainz)
23 April 2019 (online)
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.
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.
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.
Distinct alterations in of eNOS expression patterns may indicate an early intrinsic otoprotective mechanism of the inner ear after noise exposure.