Protein synthesis is not required for male pronuclear formation in bovine zygotes

Following fertilisation, the sperm triggers a series of intracellular changes which initiate oocyte activation and pronuclear formation. Oocyte activation can also be induced artificially by several chemicals, such as the calcium ionophore A23187. The sperm nucleus is transformed into the male pronucleus through the interaction of oocyte cytoplasmic factors. The profile of protein synthesis is different in bovine oocytes following fertilisation and parthenogenetic activation. The formation of male and female pronuclei was not blocked by the presence of the protein synthesis inhibitor cycloheximide. These results suggest that bovine oocyte activation by sperm and parthenogenetic activation induce different cytoplasmic responses for protein synthesis and that new protein synthesis is not required for male pronuclear formation in bovine zygotes.