Protein Synthesis in Porcine Follicular Oocytes during In Vitro Meiotic Maturation

To investigate protein synthesis associating with in vitro meiotic maturation in porcine oocytes, follicular oocytes were treated with cycloheximide (10 µg/ml) at 6 h intervals in the culture up to 48 h. Germinal vesicle breakdown(GVBD) but not chromatin condensation was blocked in the oocytes when they were treated at either 0, 6 or 12 h after culture. Also, the transition from metaphase-1 (M1) to metaphase-2(M2) was prevented. Pronuclear formation was observed in the oocytes when treated at 24 to 30 h after culture. Using [³⁵S]methionine, the profile of protein synthesis revealed that the proteins of 27, 47, 49 and 70kDa were detected only at 0 to 18 h and that new proteins of 25 and 63kDa were appeared from 24 to 48 h with presence of proteins of 39 and 92kDa throughout culture. These results suggest that in porcine oocytes GVBD and the transition from M1 to M2 require protein synthesis and that the remodelling of protein synthesis occurrs at 24 h after in vitro culture.