Effect of different chemical activation methods and electro-activation parameters on early development of porcine oocytes matured and parthenogenetically activated in vitro

The objectives were to investigate the effect of different chemical activation methods and electro-activation parameters of porcine oocytes matured and parthenogenetically activated in vitro.Porcine oocytes aspircted from local abattoir ovaries were matured in vitro for 44~48 h.Oocytes with the first polar body were activated by:(1) Different chemical methods [① 10% ethanol+ 10 μg/mL cycloheximide(CHX);② 2.5 mmol/L SrCl_2+10 μg/mL CHX;③ 5 μmol/L Ionomycin+2.5 mmol/L 6-dimethylaminopurine(DMAP);④ 200 μmol/L Thimerosal+8 mmol/L dithiothreitol(DTT);⑤ The control-no artificial activation)(Expt.1);(2) Different pulse strength and duration (Expt.2),and then were cultured for 168 h in embryo culture medium.The results indicated: (1)The rates of pronuclear formation of all treatment groups were higher than that of the control(P0.05),and the pronuclear formation rate of Ionomycin+6-DMAP group which was the highest was significantly higher(P0.05) than those of other groups;(2) The blastocyst rates of all treatment groups were higher(P0.01) than that of the control;(3) The highest rates of cleavage and blastocyst were obtained in ionomycin+6-DMAP group;(4) The SDS-PAGE protein expression profiles of porcine 4-cell parthenogenetic embryos obtained from oocytes activated by the four chemical activation methods were not significantly different;(5) The efficiency of electro-activation of porcine oocytes matured in vitro was the best when the pulse strength was 1.7 kV/cm and the pulse duration was 50 μs or 70 μs.It was concluded that:(1) All of the chemical activation protocols used in this study significantly enhanced the blastocyst development of porcine oocytes,and the combination of ionomycin and 6-DMAP was the ideal artificial activation method for porcine oocytes;(2) The SDS-PAGE protein expression profiles of porcine 4-cell parthenogenetic embryos obtained from oocytes activated by the four chemical activation methods were not significantly different;(3) At our laboratory,the optimal electric stimulation parameter for porcine oocytes matured in vitro was 1.7 kV/cm pulse strength and 50 μs or 70 μs pulse duration.