Localizations of 11ß‐hydroxysteroid dehydrogenase type 2 and mineralocorticoid receptors in the rat hypothalamus

Abstract

Mineralocorticoid receptor (MR) was found in vasopressin (VP) and oxytocin (OT) synthesizing magnocellular neurosecretory cells (MNCs) in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) in the hypothalamus. Aldosterone exerts its biological effect via MR; however, glucocorticoids also have high binding affinity to MR and substantially higher concentrations than aldosterone concentrations in the brain. An enzyme, 11β‐hydroxysteroid dehydrogenase type 2 (11β‐HSD2), converts glucocorticoid into inactive metabolites that increases aldosterone selectivity. The presence of 11β‐HSD2 has been identified in the hypothalamus; however, the specific cell types are not known. The present study which used immunocytochemical and single‐cell RT‐PCR techniques, was conducted to elucidate whether 11β‐HSD2 and MR are co‐localized in VP and OT synthesizing MNCs. Double immunofluorescence confocal microscopy demonstrated that MR and 11β‐HSD2 immunoreactivities were found in both VP‐ and OT‐immunoreactive MNCs. In addition, MR and 11β‐HSD2 mRNAs were detected in cDNA libraries derived from single MNCs. Co‐localization of MR and 11β‐HSD2 in VP and OT MNCs suggests that aldosterone directly affects the activity of VP and OT neurons through MR.NIH grant: R21 HL093728