Histochemical demonstration of 11 beta-hydroxysteroid dehydrogenase in ampullae of semicircular canals

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) plays a major role in the protection of the mineralocorticoid (type I) receptor. The cellular mechanism of aldosterone selectivity relies on the coexpression of mineralocorticoid receptors and 11 beta HSD in the same cells. An 11 beta HSD activity has been localized in the ampullae of the semicircular canal by histochemical technique which links steroid metabolism with the deposition of formazan deposition. Oxidation of 11 beta-hydroxyandrostenedione was observed in the dark cell region. Oxidation of 11 beta-hydroxyandrostenedione was nicotine-adenine dinucleotide (NAD) dependent. These results demonstrate the presence of a dehydrogenase activity separate from the nicotineamide-adenine dinucleotide phosphate (NADP) dependent 11 beta HSD.