Cochlear distribution of Na,K-ATPase and corticosteroid receptors in two mouse strains with congenital hearing disorders

As corticosteroid. hormones, via their receptors, and Na,K-ATPase are thoug ht to be involved in the regulation of endolymph production, two mouse mode ls were used to investigate whether degeneration of the stria vascularis (S V) and disturbed endolymph composition are correlated with changes in the a mounts and distribution of corticosteroid receptors and Na,K-ATPase in the cochlea. Both the shaker-2 mouse and the newly discovered mix mouse are dea f at birth and show vestibular dysfunction. In both mouse strains, the SV i s degenerated and endolymph production is severely disturbed. In the shaker -2 mouse, using the C57B1 mouse as a normal control, immunohistochemical st aining of mineralo-and glucocorticoid receptors (MR and GR) and the Na,K-AT Pase subunits alpha (1), alpha (3) and beta (1) showed a weaker reaction in all structures of the cochlea. The inner ear morphology of the mix mouse i s described and compared to that of asymptomatic, littermates. Immunostaini ng of MR, GR and the different Na,K-ATPase subunits in this mouse was consi derably weaker in the SV, while staining intensities were normal in the rem aining cochlea, The reduced corticosteroid receptor levels may lead to a re duction in Na,K-ATPase expression in the same tissues, although this conclu sion should be treated with caution. The conclusion that reduced Na,K-ATPas e levels in both mouse strains may be an important mechanism of the disturb ed endolymph production is less controversial.