Uteroglobin and other proteins in rabbit blastocyst fluid after development in vivo and in vitro

Rabbit embryos were grown in vitro from the 2- and 4-celled stage to expanded blastocysts. Proteins from the blastocysts were analyzed for specific uterine proteins as well as for bovine serum albumin (BSA), a constituent of the medium. Immunological methods revealed the presence of rabbit albumin and larger amounts of BSA. Uteroglobin, the prevailing protein fraction present in blastocyst fluid of embryos that developed in vivo was not detected in blastocysts in vitro. Prealbumin and beta-glycoprotein were also absent. From the data presented, it appears that the blastocyst does not have the capacity to synthesize detectable concentrations of uterglobin and/or other specific uterine proteins.