The Role of Ionomycin in the Improvement of in vitro Fertilization and Increasing the Rate of Bovine Embryo Development

Background: The utilization of in vitro fertilization (IVF) and in vitro embryo production (IVEP) has increased significantly as an effective tool of assisted reproductive technology. Sperm capacitation is a process of membrane maturation allowing the acrosome reaction to take place. Ionomycin is a calcium ionophore that induces the acrosome reaction by increasing calcium cycling across phospholipid membranes. The aim of this study was to enhance the cleavage rate and development of bovine embryos. Methods: Bovine ovaries were collected from the central slaughter house. Oocytes were obtained from follicles and were let to mature for 24 h. Frozen bull semen thawed in 37 degrees C water and transferred to a discontinuous percoll gradient (Sigma GE17-0891-01). The spermatozoon pellet was separated into four groups after resuspension in bovine in vitro fertilization media (BO-IVF): control without additives; with DMSO and with ionomycin (25 and 50 nM) and kept in an incubator for three hours. The oocytes matured under commonly used media (TCM-199) for 24 h. The mature oocytes were then fertilized for 18-24 h. The embryos were cultured in SOF medium until the seventh day to study cleavage rate and blastocyst rate. Result: The results indicated that 50 nM ionomycin supplementation considerably reduced cleavage while DMSO and 25 nM ionomycin supplementation had no effect on cleavage percentage. Moreover, when compared to the other groups, ionomycin at 25 nM significantly increased blastocyst development. In conclusion, the highest rate of blastocyst development was observed in the capacitation medium supplemented with 25 nM ionomycin, apparently due to the importance of calcium and metabolism in spermatozoa for fertilization and embryo development.