Activin A and inhibin B in extra-embryonic coelomic and amniotic fluids, and maternal serum in early pregnancy

Activin A and inhibin B levels were measured, using a tao-site enzyme immunoassay, in extra-embryonic coelomic fluid, amniotic fluid and maternal serum samples retrieved from 23 healthy pregnant women, at 8 (n = 8), 9 (n = 8), and 10 (n = 7) weeks of gestation. Dimeric activin A and inhibin B were measurable in all samples. Median (+/- SEM) activin A concentrations in coelomic fluid (0.98 +/- 0.34 ng/ml) were significantly higher than in maternal serum (0.68 +/- 0.05 ng/ml) and in amniotic fluid (0.09 +/- 0.04 ng/ml) (P < 0.05). Maternal serum activin A levels were significantly higher than amniotic fluid concentrations. Median(+/- SEM) inhibin B concentrations in coelomic fluid (24.32 +/- 6.02 pg/ml) were significantly higher than in maternal serum (5.94 +/- 0.97 pg/ml) and in amniotic fluid (6.31 +/- 1.53 pg/ml) (P < 0.05), while no significant difference between maternal serum levels and amniotic fluid concentrations was found. No significant difference in activin A and inhibin B levels in extra-coelomic fluid, amniotic fluid, and maternal serum throughout the 3 weeks of pregnancy was found. The present study showed that coelomic fluid is an important reservoir of activin A and inhibin B, supporting the hypothesis that the extra-embryonic coelom mag; have a secretory role during the first 11 weeks of gestation.