FATE OF INTRA-AMNIOTICALLY ADMINISTERED OESTRIOL-15-3H-3-SULPHATE AND OESTRIOL-16-14C-16-GLUCOSIDURONATE IN PREGNANT WOMEN AT MIDTERM

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Abstract
Tracer amounts of H3-labelled oestriol-3-sulphate (OE3-3S) and C14-labelled oestriol-16-glucosiduronate (OE3-16Gl) were administered intra-amniotically to two women at midterm 24 hours prior to the interruption of gestation. The radioactive metabolites present in the urine of the mother, amniotic fluid,placenta and various foetal tissues were isolated and identified. Averaging the results of the two experiments, 89% of the administeredjradioactive material was recovered. Thirty-six per cent of the H3- and 12% of the C14-labelled material was recovered from the material urine collected during the 24 hours preceding the termination of pregnancy, and an additional 14% of the H3- and 4% of the C14-labelledmaterialduring the following 96 hours. Thirty-five per cent of the H3- and 67% of the C14-labelled material administered were recovered from the foetal tissues and placenta. Three per cent of the H3- and none of the C14-labelled material administered was recovered as unconjugated ("free") material. All the unconjugated H3-labelled material recovered from the amniotic fluid and the major part of that extracted from the placenta was isolated as oestriol (OE3). Thirty-six per cent of the H3-labelled material administered was isolated from the productions of conception as OE3-3S in contrast to 70% of C14-labelled material isolated as OE3-16Gl. Some 0.2% of the Cl4-labelled material was isolated as OE3-3S and exclusively from the foetal tissues. Finally 0.5% of the H3-labelled material was isolated from the products of conception as OE3-16Gl. These data indicate that a) OE3-3S is transferred from the foetal to the maternal compartment more rapidly than OE3-16Gl, b) OE3-3S, Dut not OE3-16Gl is hydrolysed by the placenta and foetal membranes and c) in addition to the previously demonstrated sulphokinase (arylsulphotransferase, E.C. 2.8.2.1.) and glucuronyl transferase (UDPG-glucuronyl transferase, E. C. 2.4.1.17) activities also [beta] -glucuronidase ([beta]-D-glucuronide glu-curonohydrolase, E.C. 3.2.1.31.) is functioning in the foetal organism at midterm. It is concluded that since in vivo arylsulphatase (E. C 3.1.6.1.), but no [beta]-glucuronidase is functioning in the placenta and membranes, OE3-3S, but no OE3-16Gl is converted into OE3 by these tissues. Unconjugated OE3 is transferred to the maternal compartment far more rapidly than the conjugated forms. Hence OE3-3S is removed from the products of conception more rapidly than OE3-16G1, which is transferred most probably in an unchanged form. A concept is presented describing the fate of oestriol in the human foeto-placental unit at midpregnancy.