Inhibin in extra-embryonic coelomic and amniotic fluids and maternal serum in early pregnancy

Inhibins are present in maternal serum during pregnancy. However, the presence of inhibins in the compartments surrounding the fetus in early pregnancy is not well defined. Using novel specific enzyme-linked immunosorbent assays we have demonstrated that the bioactive dimeric inhibin forms, inhibin-A and inhibin-B, and the immunoreactive inhibin forms containing pro- and αC sequences are present in different amounts in the extra-embryonic coelomic and amniotic fluids and maternal serum between 8-11 weeks gestation. Of the bioactive dimeric inhibins, both inhibin-A (mean ± SEM 236.0 ± 24.8 pg/ml) and inhibin-B (62.0 ± 8.6 pg/ml) are present in extra-embryonic coelom, whereas no dimeric inhibin is present in the amniotic fluid and only inhibin-A (360.2 ± 32.9 pg/ml) is present in maternal serum. Furthermore, pro-αC-related immunoreactivity is present at high concentrations in the extraembryonic coelom (591.7 ± 60.5 pg/ml), amniotic fluid (452.4 ± 76.8 pg/ml) and maternal serum (539.4 ± 39.5 pg/ml). These findings would indicate that at this stage of gestation inhibin-A, inhibin-B and immunoreactive pro-αC-containing inhibin production are likely to arise from different sources including the fetus, placenta and fetal membranes and maternal sources including the ovary. Inhibins may be important regulators of fetal and placental development and involved in the establishment of inhibin assays, to establish the origin and ontogeny of inhibin pregnancy.