PROTEIN AND ENZYME PATTERNS IN THE FLUID CAVITIES OF THE FIRST-TRIMESTER GESTATIONAL SAC - RELEVANCE TO THE ABSORPTIVE ROLE OF SECONDARY YOLK-SAC

The potential absorptive role of the yolk sac membrane was evaluated b y examining protein and enzyme patterns in embryonic fluids and by com paring the synthetic capacity of the secondary yolk sec, fetal liver a nd placenta for human chorionic gonadotrophin (HCG) and alpha-fetoprot ein (alpha FP). In yolk sac fluid samples, protein electrophoresis sho wed two main electrophoretic bands with mobilities comparable to those of albumin and interalbumin-alpha 1-globulin, and immunoblotting reve aled the presence of albumin, alpha FP, alpha 1-antitrypsin, alpha 2-m acroglobulin. transferrin, complement factors 3 and 4 and immunoglobul in G. In coelomic fluid, similar results were obtained, except for the absence of alpha 2-macroglobulin and the presence of ceruloplasmin an d IgA, After electrophoresis and immunoblotting with specific antibodi es, beta-HCG was detected in all placental homogenates and culture med ia but was not revealed in any of the corresponding yolk sec tissue sa mples. Reverse transcription-polymerase chain reaction (RT-PCR) showed that all placental samples express beta-HCG mRNA whereas all yolk sec and liver samples express alpha FP mRNA. These findings suggest that the yolk sec membrane is an important zone of transfer between the ext ra-embryonic and embryonic compartments and may also help to further d evelop therapeutic protocols making use of fetal somatic gene therapy by injecting transduced cells into the exocoelomic cavity.