11β-Hydroxysteroid Dehydrogenase Type II and Mineralocorticoid Receptor in Human Placenta1

Abstract

In mineralocorticoid target organs, 11-hydroxysteroid dehydro-genase type II (11-HSD2) confers specificity on the mineralocorticoid receptor (MR) by converting biologically active glucocorticoids to inactive metabolites. Placental 11-HSD2 is also thought to protect the fetus from high levels of circulating maternal glucocorticoid. In this study, we examined the immunoreactivity of 11-HSD2 and MR in human placenta from 5 weeks gestation to full term using immuno-histochemistry, 11-HSD2 messenger RNA (mRNA) expression using Northern blot analysis, and MR mRNA expression using RT-PCR analysis. Marked 11-HSD2 immunoreactivity was detected in pla-cental syncytiotrophoblasts at all gestational stages. MR immunore-activity was moderately detected in syncytiotrophoblasts, some cy-totrophoblasts, and interstitial cells of the villous core. Marked mRNA expression of 11-HSD2 was detected in placenta by Northern analysis. RT-PCR analysis of MR in placental tissues showed an amplified product consistent in length with the primers selected. These results suggest that placental 11-HSD2 is involved in not only regulating the passage of maternal active glucocorticoids into the fetal circulation but also in regulation of maternal-fetal electrolyte and water transport in the placenta, as in other mineralocorticoid target organs. (