Prenatal low-dose gamma irradiation of the inner ear induces changes in the expression of intermediate filaments.

The expression of intermediate filaments (1F) was analysed in the inner ear in normally developed adult CBA/CBA mice and in mice of the same age which had been gamma irradiated in utero with a low dose 1-2 Gy single exposure. Well characterized monoclonal antibodies (mAbs) against all classes of intermediate filament proteins (cytokeratins-Cks, vimentin, neurofilaments, desmin and glial fibrillar acidic protein) were used. With the exception of neurofilament proteins, the expression of intermediate filament proteins was the same in adult normal and irradiated inner ears, irrespective of gestational age at exposure. A complex Ck pattern occurred in the various cell types comprising the membranous labyrinth. In spite of the differences in cell shape and internal organization of organelles, epithelia actively involved in inner ear fluid homeostasis (stria vascularis, dark cell epithelium, endolymphatic duct and sac) revealed, according to our mAbs, the same expression of Cks, except for the mouse counterpart of human Ck 7, which was found exclusively in the stria vascularis and the endolymphatic duct and sac. The pattern of intermediate filament composition in the labyrinth was the same in the mouse as in man. Irradiation on gestational days 12 or 13 (the otocyst stage)--but not at more advanced embryonic age--induced immunoreactivity for neurofilament proteins in vestibular hair cells (HC) and to a minor extent also in cochlear HC. No such positivity was found in the control material.