Abstract: The objective of this study was to determine the effects of ionomycin combined with cytochalasin B (CB), cycloheximide (CHX), or 6-dimethylaminopurine (6-DMAP) on the activation of porcine oocytes. In experiment 1, in vitro matured oocytes were activated with ionomycin at 15, 20, 25 or 30 mol·L-1. Activation rates of 20, 25 mol·L-1 and 30 mol·L-1 treatments were higher （P<0.05）than that of 15 mol·L-1 treatment. In experiment 2, in vitro matured oocytes were activated with 20 mol·L-1 ionomycin at 10,20,30,40 or 50 min and then incubated with 2 mmol·L-1 6-DMAP 6 h.Cleavage rates and blastocyst formation rates after 40 min treatments [(72.40±13.02)%, (25.37±11.43)%]was higher (P>0.05) than that of the either treatments. In experiment 3, matured oocytes were activated with ionomycin and then incubated with 7.5 g·ml-1 CB,10 g·ml-1 CHX, 2 mmol·L-1 6-DMAP, 7.5 g·ml-1 CB +10 g·ml-1 CHX or 7.5 g·ml-1 CB +2 mmol·L-1 6-DMAP for 6 h. Activation rates, cleavage rates and blastocyst formation rates of 2 mmol·L-1 6-DMAP treatment [(86.05±4.29)%, (61.77±8.10)% and (21.62±3.31)%] was higher (P<0.05) than that of 7.5 g·ml-1 CB treatment. In experiment 4, matured oocytes were activated with ionomycin and then incubated with 2 mmol·L-1 6-DMAP for 3.5, 5.5 or 7.5 h. Cleavage rates and blastocyst formation rates of 5.5 h treatment [(66.59±14.36)% and (25.40±10.16)%] was higher (P>0.05) than that of other treatments. In conclusion, activation of porcine oocytes appears to be most successful using the combination of ionomycin (20 mol·L-1, 40 min) followed by 6-DMAP (2 mmol·L-1 , 5.5 h).

Key words: Porcine, Oocyte, in vitro maturation, Parthenogenetic activation, Ionomycin