11 beta-hydroxysteroid dehydrogenase type 2 and mineralocorticoid receptorin human fetal development

11 beta-Hydroxysteroid dehydrogenase type II (11 beta HSD2) confers specifi city on the mineralocorticoid receptor (MR) by converting biologically acti ve glucocorticoids to inactive 11-keto metabolites. The biological signific ance of 11 beta HSD2 activity during fetal development is currently being e xplored, but the temporal and spatial distributions of the enzyme and recep tor have not been examined. We therefore examined their distributions durin g Various stages of human fetal development using immunohistochemistry. Bat h 11 beta HSD2 and MR immunoreactivity were detected in the distal convolut ed and collecting tubules of the kidney from early in gestation. Fetal skin , intermediate layer of the epidermis, peridermal cells, and hair follicles were positive for both 11 beta HSD2 and MR. Weak 11 beta HSD2 and MR immun oreactivity was detected in the superficial ciliated epithelium of the esop hagus, the deep layer of gastric epithelial cells, and the superficial epit helium of the small intestine. Columnar epithelium in the terminal bronchio lar budding component of fetal lung and tracheal and bronchial ciliated epi thelium were also positive for MR and 11 beta HSD2 from early gestation. Co lonic epithelium and pancreatic exocrine duct cells, which demonstrated mar ked immunoreactivity of both MR and 11 beta HSD2 in the adult, did not expr ess MR and 11 beta HSD2 until very late in gestation. These results imply t hat mineralocorticoid action in the upper fetal gastrointestinal tract, kid ney, shin, and lung is facilitated by 11 beta HSD2 and is involved in water and electrolyte transport between fetus and amniotic fluid as well as feta l urine production.