Protein degradation during preimplantation development of the mouse

Summary. The half-lives of labelled proteins were determined for mouse preimplan-tation embryo stages from the germinal vesicle oocyte to the early blastocyst. While no significant differences were found among half-lives for 1-cell stages, or among half-lives for cleavage stages, a significant (P < 0\m=.\05)28 % decrease in half-life was observed between the 1-cell and the cleavage stages. Labelled protein half-lives were 18\m=.\2and 13\m=.\1h for the 1-cell and cleavage stages respectively. Fertilization probably initiates this increase in protein degradation rate although no significant decrease was detected until after the first cleavage