Development of preimplantation rabbit embryos in vivo and in vitro

Qualitative patterns of protein synthesis in preimplantation rabbit embryos grown in vivo and in vitro were examined by SDS polyacrylamide gel electrophoresis followed by autoradiography. The results demonstrate that (1) most qualitative changes in the pattern of protein synthesis occur during cleavage, (2) the blastocyst period of development is characterized by a remarkably uniform and constant pattern of protein synthesis, and (3) the qualitative pattern of protein synthesis in embryos cultured in vitro from the 1-cell to the blastocyst stage is essentially identical to the pattern of protein synthesis in embryos grown to a comparable stage in vivo.These results indicate that no “special” maternal factors, such as uterine proteins, are required in vitro either for the qualitative changes in the pattern of protein synthesis during cleavage, or for the initial expression of a pattern of protein synthesis characteristic of the entire blastocyst period. From these studies we conclude that, once fertilized, the rabbit egg proceeds through cleavage and blastocyst formation on its own endogenous developmental program.