Activation of pig oocytes using calcium ionophore: effect of the protein kinase inhibitor 6-dimethyl aminopurine

The aim of our study was to investigate the parthenogenetic activation of in vitro matured pig oocytes after their combined treatment with calcium ionophore A 23187 and the inhibitor of protein kinases, 6-dimethylaminopurine (6-DMAP) and to study the further embryonic development of oocytes activated using this treatment. The oocytes were exposed to ionophore (10, 25 or 50 microM) for 0.5, 1, 3, 5 or 7 min and then cultured with 6-DMAP (0 or 2 microM) The highest activation rate (up to 88% of the activated eggs reached the pronuclear stage) was observed after combined treatment of the oocytes with 50 microM ionophore and 6-DMAP. The highest rate of embryonic development was observed after treatment with 25 microM ionophore without 6-DMAP, when up to 51% of the eggs developed beyond two-cell stage, 2% of the eggs developed up to the stage of morula and up to 3% of the eggs reached the stage of blastocyst. When 50 microM ionophore was used, the embryonic development of the activated eggs was arrested before the morula and blastocyst stage. After treatment of the activated eggs with 6-DMAP, we did not observe any development beyond the stage of 16 blastomeres. We can conclude that combined treatment with calcium ionophore A 23187 and 6-DMAP increases the activation rate in pig oocytes matured in vitro, but this combined treatment exerts a detrimental effect on further embryonic development of the activated eggs.