LIPOPOLYSACCHARIDE-INDUCED EXPRESSION OF REACTIVE OXYGEN SPECIES AND PEROXYNITRITE IN THE GUINEA-PIG VESTIBULAR ORGAN

The purpose of this study was to investigate the occurrence of reactiv e oxygen species and peroxynitrite in the vestibular organ of the guin ea pig following inoculation with bacterial lipopolysaccharide (LPS). The animals were injected transtympanically with 1 mg of LPS 24 h afte r the intraperitoneal injection of 0.1 mg LPS. Forty-eight hours after the inoculation, varying degrees of degeneration of the vestibular en d organs were observed. Immunohistochemical study revealed immunoreact ivity to xanthine oxidase (which generates O-2(-)) in the vestibular o rgan after inoculation with LPS. Immunohistochemical. investigation wi th a specific antinitrotyrosine antibody also showed intense staining of sensory epithelium, fluid transporting cells and the endolymphatic sac, suggesting formation of peroxynitrite in the vestibular organ thr ough the reaction of NO with O-2(-). On the basis of these data, it ca n be concluded that NO together with O-2(-) which form more reactive p eroxynitrite, may be the most important pathogenic agents in LPS-induc ed labyrinthitis in the guinea pig.