Intermediate filament proteins in the embryonic inner ear of mice under normal conditions and after exposure to ototoxic drugs.

The expression of the intermediate filament subclasses cytokeratins (CKs), vimentin, and neurofilament triplet proteins (NFs) was analysed in the embryonic inner ear of the CBA/CBA mouse, in vivo and in vitro, using well-defined monoclonal antibodies. Some of the cultured inner ears were exposed to 1-10 micrograms/ml of the ototoxic drugs gentamicin, ethacrynic acid or cisplatin. There was no difference in the expression of IF pattern in the cultured inner ears as compared with the in vivo developed labyrinths. Exposure to the ototoxic drugs did not affect the expression of CKs, vimentin, or NFs. CKs 8 and 18 were identified in all inner ear epithelia. In the mature hair cells, only the apical surfaces showed immunoreactivity to CKs. In addition, CKs 7 and 19 were visualized in the epithelia involved in maintaining endolymph homeostasis. The ganglion cells showed co-expression of CKs, vimentin and NFs, each having a characteristic localization in the cells.