This medium contains 7.5 mM extracellular Ca2+, which is a concentration much higher than that used in previous studies. We found that most parameters (peak ratio value of Ca2+ transient, CG exocytosis, and nuclear activation) measured in the present study were concentration-dependent; i.e., higher concentrations of A23187 induced a higher ratio of Ca2+ transient, which in turn induced higher rates of CG exocytosis and nuclear activation. The differences observed in the present study from previous reports may be due to the composition (such as concentration of calcium) of the media used by different researchers or the quality of oocytes matured under different conditions. The oocytes matured in our present study can develop to blastocysts (-30% of blastocyst formation of inseminated oocytes) after IVF/in vitro development and also to term after IVF/embryo transfer. It is well-known that cytoplasmic maturation is significantly affected by the culture conditions in pig oocytes. Various cytoplasmic factor(s) may affect the response of oocytes to external stimulators. buy diabetes drugs
On the other hand, bat-star Patina miniata, Xenopus laevis, hamster Mesocricetus auratus, and sea urchin oocytes can be activated by A23187 in Ca2+-free medium, and it is suggested that mobilization of the oocyte’s own calcium stores is sufficient to stimulate CG exocytosis and nuclear activation.