Protein synthesis in vivo by preimplantation hamster embryos

The level of protein synthesis by hamster embryos in vivo, as inferred from the incorporation of ³⁵S methionine, was determined for the four days of the preimplantation period by radioautography. The embryos incorporated ³⁵S methionine throughout the preimplantation period. Furthermore, the hamster eggs continued to incorporate ³⁵S methionine following ovariectomy. Therefore, the pattern of protein synthesis in hamster eggs differs from the mouse with its low levels in cleaving eggs and in blastocysts following ovariectomy and high levels in blastocysts influenced by estrogen and progesterone. This finding is of interest because unimplanted mouse embryos remain viable in ovariectomized females for many days, whereas hamster embryos rapidly degenerate. It is suggested that the inability of hamster eggs to reduce the level of protein synthesis and become “dormant” may prevent their survival if implantation is blocked by ovariectomy.