4 人の胎児-胎盤系におけるestriol生合成経路
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概要
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It has been well known that there are two pathways to estriol (E3) from dehydroepiandrosterone (DHEA) in the feto-placental compartment. In A-pathway, in which the aromatization of DHEA in the placenta is antecedent and the 16 a-hydroxylation of estrone (El) in the fetus is followed, E3 is mainly formed in the fetal liver. In B-pathway, in which the 16α-hydroxylation of DEHE in the fetus is antecedent and the aromatization of 16α-hydroxy-C 19 steroids in the placenta is followed, E3 is finally formed in the placenta. The B-pathway is subdivided into B-1 and B-2 pathways. In the B-1 pathway, 16α-hydroxy-DEHA is first formed in the fetal adrenal or liver, and then E3 is formed through 16α-hydroxyandrostenedione and 16α-hydroxy-El in the placenta. In the B-2 pathway, androstenetriol is first formed in the fetal liver, followed by the formation of E3 through 16-hydroxytestosterone in the placenta.<BR>In an attempt ot clarify the main pathway to E3 from DHEA in the feto-placental unit, H<SUP>3</SUP>-DHEA and C<SUP>14</SUP>-androstenedione were administered into the umbilical blood in two cases of midpregnant women in which interruption of preganancy was performed by cesarean section for medicosocial reasons.<BR>The radioactive metabolites in the placenta, umbilical blood, fetal liver and maternal urine obtained 15 minutes later were analyzed. In the case 1, the <SUP>3</SUP>H/C<SUP>14</SUP> ratios of E3 in the placenta, umbilical blood and fetal liver were 5.5, 9.5 and 1.7, respectively. The respective ratios of El were 3.0, 1.0 and 0.9; those of 16α-hydroxy-E1 were 1.6, 1.0 and 1.0, respectively. The The <SUP>3</SUP>H/C<SUP>14</SUP> ratios of 16α-hydroxytestosterone in the placenta and umbilical blood were 19.8 and ∞, respectively. The <SUP>3</SUP>H/C<SUP>14</SUP> ratios of various steroids in the case 2 were comparatively the same as those in the case 1. In the placenta and umbilical blood, the <SUP>3</SUP>H/C<SUP>14</SUP> ratios of E<SUB>3</SUB> were markedly higher than those of 16α-hydroxy-E1. In constrast, the ratio of E3 in the fetal liver was almost the same as that of 16α-hydroxy-El. Furthermore, the quantity of E3 in the placenta and umbilical blood is approximately 2 times that in the fetal liver.<BR>From these data, one could draw the following conclusion;<BR>1) In the feto-placental compartment, E3 might be formed in the placenta in large quantities and in the fetal liver in smaller quantities.<BR>2) E3 in the placenta and umbilical blood might be mainly formed from DHEA via 16α-hydroxytestosterone (B-2 pathway).<BR>3) E3 in the fetal liver might be mainly formed from DHEA via El and 16α-hydroxy-El (A-pathway).
- 一般社団法人 日本内分泌学会の論文