Determination of protein pattern in embryonic cavities of human early pregnancies: a means to understand materno-embryonic exchanges

Exocoelomic and amniotic fluids were obtained by selective puncture under ultrasound guidance in normal human pregnancies between 5 and 13 weeks of gestation. Evaluation of the protein patterns in the exocoelomic fluid showed qualitative and quantitative changes with advancing gestation. During the second month of gestation, three electrophoretic bands were found with mobility compatible with albumin, α1-globulin and β-globulin and composed of at least eight proteins including: pre-albumin, albumin, α-fetoprotein (α-FP), α1-protease inhibitor, haptoglobin, ceruloplasmin, transferrin and immunoglobulin-G, as revealed by immuno-blotting. Protein patterns obtained between 9 and 13 weeks were comparable in exocoelomic fluid and in maternal serum except for the presence of α-FP in the α1-globulin band. At the same gestational age, protein electrophoresis of amniotic fluid revealed four bands corresponding to albumin, α-FP, haptoglobin and transferrin. Creatinine levels were significantly lower (P < 0.01) in amniotic fluid than in exocoelomic fluid, and α-FP levels were similar in both exocoelomic and amniotic fluids. These results suggest that the exocoelomic fluid is a transudate of the maternal serum except for the presence of high levels of α-FP, that amniotic and exocoelomic cavities are separated by a non-permeable membrane and that the secondary yolk sac plays an important role in early protein synthesis and transfer.