17 beta-hydroxysteroid dehydrogenase type 1 and 2 expression in the human fetus

The present study investigates the expression patterns of 17 beta-hydroxyst eroid dehydrogenase (17 beta HSD) isozymes in human fetal tissues to unders tand how estrogenic activity is regulated in the human fetus. Using enzyme assay, high 17 beta HSD activity was detected in the placenta and liver, an d low levels of 17 beta HSD activity were also present in the gastrointesti nal tract and kidney. After Northern blot analysis, we detected the messeng er ribonucleic acid for 17 beta HSD type 1 (17 beta HSD1) only in the place nta, whereas that for 17 beta HSD type 2 (17 beta HSD2) was detected in the placenta, Liver, gastrointestinal tract, and urinary tract at 20 gestation al weeks. In RT-PCR analysis of the messenger ribonucleic acid transcripts, 17 beta HSD 1 was predominantly expressed in the placenta, brain, heart, l ung, and adrenal, whereas 17 beta HSD2 expression was predominantly detecte d in the liver, gastrointestinal tract, and kidney. In addition, we detecte d 17 beta HSD2 immunoreactive protein in surface epithelial cells of the st omach, absorptive epithelial cells of the small intestine and colon, hepato cytes of the liver, and interstitial cells surrounding the urinary tubules of the renal medulla. 17 beta HSD2 in these tissues may be functioning in t he prevention of in utero exposure of the fetus to excessive estradiol from the maternal circulation and amniotic fluids.