In vitro synthesis of estrogens by midterm human placenta and fetal liver

Radioactive progesterone, 17α-hydroxypregnenolone, androstenedione and testosterone were incubated with midterm human fetal liver and placenta. After isolation of the radioactive phenolic metabolites, purification was achieved by paper chromatography and crystallization to constant specific activity. Fetal liver converted androstenedione and testosterone to estrone, 17β-estradiol and estriol. Estriol, but no estrone and 17β-estradiol could be identified from the incubation of progesterone and 17α-hydroxy-pregnenolone. The corresponding midterm placenta readily aromatized androstenedione and testosterone to estrone, 17β-estradiol and estriol. The conversion of progesterone and 17α-hydroxypregnenolone to estrogens was small and varied between 0.2 and 0.34%.