Abstract
ABSTRACT Two midgestation placentas were perfused with 2.5 mCi of uniformly labelled 14C-sodium acetate plus 2.5 mCi cholesterol-7α-3H. and two complete foeto-placental units were perfused with 5.0 mCi of 14C-labelled sodium acetate plus 5.0 mCi of cholesterol-7α-3H. The perfusions were carried out at 35–36°C for 90 min. After the perfusion of the isolated placentas, the following 3H-labelled steroids were isolated from the placentas as well as from the perfusates in a radiochemically homogeneous form: pregnenolone (3β-hydroxy-pregn-5-en-20-one), progesterone (pregn-4-ene-3,20-dione), 20α-dihydroprogesterone (20α-hydroxy-pregn-4-en-3-one), 20β-dihydroprogesterone (20β-hydroxy-pregn-4-en-3-one), 17α-hydroxy-pregnenolone (3β,17α-dihydroxy-pregn-5-en-20-one),dehydroepiandrosterone(3β-hydroxy-androst-5-en-17-one) and 17β-oestradiol (oestra-1,3,5(10)-triene-3,17β-diol). The same compounds were also isolated from the placentas following the perfusion of the complete foeto-placental units. With the exception of pregnenolone and progesterone, all steroids were isolated in minute quantities. None of the steroids isolated contained any 14C-label. It is concluded that the midgestation human placenta is not capable of carrying out any de novo steroid synthesis from acetate and that cholesterol is an obligatory precursor in placental steroidogenesis.
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