11-BETA-HYDROXYSTEROID DEHYDROGENASE IN THE RAT INNER-EAR

beta-Hydroxysteroid dehydrogenase (11 beta-HSD) was demonstrated speci fically in the spiral ligament of the cochlear membranous labyrinth by enzyme assay, Western blotting, and immunocytochemistry. Other cochle ar regions and the vestibular membranous labyrinth were devoid of 11 b eta-HSD. Spiral ligament 11 beta-HSD exerted predominantly an oxidativ e activity and was NADP specific, which is similar to 11 beta-HSD in m ost other tissues. 11 beta-HSD was colocalized with mineralocorticoid and glucocorticoid steroid receptors in the spiral ligament. 11 beta-H SD may control steroid binding to these inner ear steroid receptors an d, in addition, may regulate steroid receptor binding in the adjacent stria vascularis in paracrine fashion.