Abstract
Bovine yolk sac at day 24 of pregnancy, and placental membranes (chorion and allantois) from days 70 and 100 of pregnancy were isolated and cultured in a modified minimum essential medium in the presence of ( 35 S)methionine. Proteins synthesized and secreted by isolated bovine yolk sac, chorion and allantois were analyzed by fluorography of two-dimensional polyacrylamide gel electrophoresis. Serum-like proteins,transferrin, α-fetoprotein, α1-antitrypsin and α1-acid glycoprotein ,were the major protein products of yolk sac. A 21 kDa protein produced by yolk sac was identified immunochemically as retinol-binding protein (RBP). Chorion and allantios from days 70 and 100 of pregnancy were active in protein synthesis and secretion. Both chorion and allantois did not secret serum-like proteins but secreted a number of neutral-to-acidic proteins including RBP. Secretory proteins produced by the yolk sac, chorion and allantois may play important roles in the embryonic development and the successful outcome of pregnancy. Antiserum against bovine placental RBP was employed to the immunocytochemistry by immunoperoxidase method. Immunoreactive RBP was localized in epithelial cells and island-like cell clones of yolk sac. Immunostaining for RBP was detected in simple columnar epithelium of chorion and in simple squamous epithelium of allantois. In the present study, proteins synthesized and secreted by yolk sac at day 24 of pregnancy, chorion and allantois from days 70 and 100 of pregnancy were characterized In addition, RBP was localized in yolk sac, chorion and allantois by immunoperoxidase method. The immunoperoxidase method has been proven to be a very effective technique to identify the cellular source of protein synthesis in extraembryonic membranes. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 6 : 783- 788)
Highlights
In bovine, after onset of estrus, fertilization occurs on day 1 in the oviduct, at the ampullary-isthmic junction (Hunter, 1985)
The outer layer of mesoderm lines the trophectoderm to form the chorion while the inner layer covers the endoderm to constitute the wall of the yolk sac (Greenstein and Foley, 1958)
Secretory proteins produced by the yolk sac, chorion and allantois may be relevant to the embryonic development and the successful outcome of pregnancy
Summary
Proteins synthesized and secreted by isolated bovine yolk sac, chorion and allantois were analyzed by fluorography of two-dimensional polyacrylamide gel electrophoresis. Chorion and allantios from days 70 and 100 of pregnancy were active in protein synthesis and secretion. Both chorion and allantois did not secret serum-like proteins but secreted a number of neutral-to-acidic proteins including RBP. Proteins synthesized and secreted by yolk sac at day 24 of pregnancy, chorion and allantois from days 70 and 100 of pregnancy were characterized In addition, RBP was localized in yolk sac, chorion and allantois by immunoperoxidase method.
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