11 beta-hydroxysteroid dehydrogenase type II and mineralocorticoid receptor in human placenta

In mineralocorticoid target organs, 11 beta-hydroxysteroid dehydrogenase ty pe II(11 beta-HSD2) confers specificity on the mineralocorticoid receptor ( MR) by converting biologically active glucocorticoids to inactive metabolit es. Placental 11 beta-HSD2 is also thought to protect the fetus from high l evels of circulating maternal glucocorticoid. In this study, we examined th e immunoreactivity of 11 beta-HSD2 and MR in human placenta from 5 weeks ge station to full term using immunohistochemistry, 11 beta-HSD2 messenger RNA (mRNA) expression using Northern blot analysis, and MR mRNA expression usi ng RT-PCR analysis. Marked 11 beta-HSD2 immunoreactivity was detected in pl acental syncytiotrophoblasts at all gestational stages. MR immunoreactivity was moderately detected in syncytiotrophoblasts, some cytotrophoblasts, an d interstitial cells of the villous core. Marked mRNA expression of 11 beta -RSD2 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 beta-HSD2 is involved in not only regulating the passage of maternal active glucocortico ids into the fetal circulation but also in regulation of maternal-fetal ele ctrolyte and water transport in the placenta, as in other mineralocorticoid target organs.