HISTOCHEMICAL-DEMONSTRATION OF 11-BETA-HYDROXYSTEROID DEHYDROGENASE IN AMPULLAE OF SEMICIRCULAR CANALS

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) plays a major sole in the protection of the mineralocorticoid (type I) recepto r. The cellular mechanism of aldosterone selectivity relies on the coe xpression of mineralocorticoid receptors and 11 beta HSD in the same c ells. An 11 beta HSD activity has been localized in the ampullae of th e semicircular canal by histochemical technique which links steroid me tabolism with the deposition of formazan deposition. Oxidation of 11 b eta-hydroxyandrostenedione was observed in the dark cell region. Oxida tion of 11 beta-hydroxyandrostenedione was nicotine-adenine dinucleoti de (NAD) dependent. These results demonstrate the presence of a dehydr ogenase activity separate from the nicotineamide-adenine dinucleotide phosphate (NADP) dependent 11 beta HSD.