Immunocytochemical Localization of Intermediate Filaments in the Guinea Pig Vestibular Periphery with Special Reference to Their Alteration after Ototoxic Drug Administration

The present study examined the immunocytochemical localization of various intermediate filaments (IFs). 68 kDa. 160 kDa and 200 kDa neurofilament protein (NFP). cytokeratin (CK) 1, 8, 10 and 19, vimentin, and glial fibrillary acidic protein (GFAP) in the vestibular endorgans and ganglia of normal and streptomycin-treated guinea pigs. In normal animals, 68 kDa, 160 kDa and 200 kDa NFP were found in afferent nerve fibers and nerve terminals (probably nerve chalices). Fine nerve fibers (probably efferent and/or sympathetic nerve fibers) were also immunoreactive to NFP. In the vestibular ganglia, 68 kDa and 160 kDa NFP were predominantly distributed in larger cells, whereas 200 kDa NFP was also found in some small ganglion cells. Cytokeratin 8 and 19 were located in supporting cells, transitional cells, dark cells of vestibular endorgans. and the epithelial cell lining of the membranous labyrinth. Vimentin was observed in the hair cells distributed in the central region of the end organs, supporting cells, most connective tissue cells, and Schwann cells of the vestibular ganglion. Although GFAP-like immunoreactivity was evident in glial cells of the proximal vestibular nerve, no immunoreactivity was detected in the distal portion of the vestibular nerve, vestibular ganglion, or vestibular endorgans. These highly distinct staining patterns of IFs indicated that they may play different roles in the different cell types, and that they may serve as a specific marker for each cell type. In streptomycin-treated guinea pigs, immunoreactivities for NFP and vimentin (found in the hair cells) decreased after treatment, whereas immunoreactivities for the other IFs were not affected. These results suggested that neuronal cytoskeletal components are the most vulnerable IFs to this ototoxic drug.