Serum protein depletion by cultured post-implantation rat embryos.

Four rat serum proteins were found to be selectively depleted from the culture medium by 10 day rat embryos. These were alpha 2-macroglobulin, transferrin and 2 other proteins which had molecular weights of 132,000 and 214,000. Possibly a 5th protein, alpha 1-acid glycoprotein, was also depleted but its concentration was already low at the start of culture.