Follistatin and activin A in extra-embryonic coelomic and amniotic fluids and maternal serum in early pregnancy

Follistatin is a specific binding protein which controls bioavailability of activins and inhibins which have an important role in fetal development. I n the first trimester of pregnancy bioactive dimeric inhibins are found at high concentrations in the extra-embryonic coelomic fluid, but the distribu tion of follistatin and activins is not known. We have used recently develo ped immunoassays for follistatin, activin A and activin AB to determine the ir presence in the intrauterine compartments during early pregnancy. Follis tatin was present in highest concentrations in the extra-embryonic coelomic fluid (11.72 +/- 1.70 ng/ml; median +/- SEM), with less in maternal serum (6.35 +/- 4.58) and lowest amounts in amniotic fluid (0.97 +/- 0.52), Folli statin concentrations in extra-embryonic coelomic fluid were highly correla ted with both dimeric inhibin isoforms, Activin A was present in only barel y detectable amounts in some samples of extra-embryonic coelomic fluid (41% of samples) and maternal serum (26%) and was undetectable in all amniotic fluid samples. Activin AB was undetectable in all compartments. The presenc e of follistatin in the amniotic and extra-embryonic coelomic fluids may re gulate the availability of bioactive activins and inhibins which are releas ed into the intrauterine compartments during the development of the fetus a nd placenta in early pregnancy.