STUDIES ON THE METABOLISM OF C-21 STEROIDS IN THE HUMAN FOETO-PLANCENTAL UNIT

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Abstract
Human placentas were perfused in situ at midpregnancy with labelled progesterone, 20α-dihydroprogesterone and 20β-dihydroprogesterone and the radioactive material recovered from the placentas and perfusates was analysed. Placental metabolism of progesterone was rather limited; a small amount was transformed into 20α-dihydroprogesterone and into 6β-hydroxyprogesterone. No conversion into 16α-hydroxyprogesterone, 17α-hydroxyprogesterone, deoxycorticosterone, androstenedione, 20β-dihydroprogesterone or pregnanediol was found. 20α-Dihydroprogesterone was extensively converted into progesterone and, to a small extent, into 6β-hydroxyprogesterone. These conversions could not be demonstrated with 20β-dihydroprogesterone. A scheme is presented describing the placental metabolism of progesterone and of its 20α- and 20β-reduced forms.