Aromatisation of androstenedione and testosterone by the human fetus

Abstract Two male and two female previable human fetuses (18th to 20th week of gestation) were perfused with a combination of 3 H-labelled testosterone (17β-hydroxyandrost-4-en-3-one) and 14 C-labelled androstenedione (androst-4-ene-3, 17-dione). Following reduction with potassium borohydride, E 2 (estra-1,3–5(10)-triene-3, 17β-diol) was isolated in a radiochemically homogeneous form from the phenolic fraction obtained after solvolysis of the water-soluble, ether-insoluble radioactive material present in the liver. The isolated E 2 accounted for 0.7 to 5.8 per cent of the total radioactive material recovered from the liver. In every case more androstenedione than testosterone was converted into E 2 + e 1 (3-hydroxyestra-1, 3,5(10)-trien-17-one). Two female fetuses were perfused with a combination of 3 H-labelled DHA (3β-hydroxy-androst-5-en-17-one) and 14 C-labelled androstenedione. No 3 H-label, only 14 C was present in the E 2 isolated from the liver. E 2 constituted 2.9 and 6.2 per cent, respectively, of the total radioactive material recovered from the liver. It is concluded that human fetuses of both sexes at midterm possess the capacity of aromatising androstenedione and testosterone, but that they lack the ability to aromatise DHA. A concept is presented describing the formation of E 1 and E 2 in the human feto-placental unit at midpregnancy.