PROTEIN AND STEROID-LEVELS IN EMBRYONIC CAVITIES IN EARLY HUMAN-PREGNANCY

Biochemical analysis including concentrations of urea, creatinine, human chorionic gonadotrophin (HCG), oestradiol, progesterone, and alpha-fetoprotein (AFP), two-dimensional gel electrophoresis, and the affinity of AFP for Concanavalin A (Con A)-Sepharose were performed on samples of exocoelomic and amniotic fluids retrieved by transvaginal puncture and maternal serum from 25 normal pregnancies between 5 and 12 weeks of gestation. Biochemical assays showed that during this period of gestation no differences in urea concentration were found between fluids from the three compartments, whereas creatinine concentration decreased significantly (P < 0.001) from maternal serum to amniotic fluid. The exocoelomic fluid contained significantly (P < 0.001) higher concentrations of oestradiol, progesterone and HCG than both maternal serum and amniotic fluid. AFP concentration was similar in amniotic and exocoelomic fluids and significantly (P < 0.001) lower in maternal serum. Between the second and the third months of gestation, urea concentration decreased significantly (P < 0.05) and oestradiol, HCG and AFP increased significantly in maternal serum (P < 0.05, P < 0.05, P < 0.001, respectively). During the same period of gestation, exocoelomic fluid concentrations of urea and HCG decreased significantly (P < 0.005, P < 0.001, respectively). Comparison of the two-dimensional gel patterns obtained from maternal serum with those from exocoelomic amniotic fluids revealed no significant qualitative differences, except for several small proteins. These results suggest that protein pathways across materno-embryonic membranes are not simply passive transfers. Con A affinity molecular variants of AFP demonstrated that both exocoelomic and amniotic fluid AFP were mainly of yolk sac origin and that maternal serum AFP was mainly of fetal liver origin, suggesting that the human secondary yolk sac has both absorptive and excretory functions.