Mohamad Reza Darabi - Department of Anatomy, Arak University of Medical Sciences, Arak, Iran.
Mohamad Hosein Nasr-Esfahani - Department of Clinical and Experimental Embryology, Reproductive Medicine Research Center, Royan Institute, Isfahan campus, ACECR Tehran, Iran.
Hosein Baharvand - Department of stem cell, Royan Institute, Tehran, Iran.
Mohmad Mardani - Department of Anatomy, Isfahan University of Medical Sciences, Isfahan, Iran.

Background: The values of embryonic stem cell and cloning are evident. Production of clone from embryonic stem cells can be achieved by introduction of stem cell into atetraploid blastocyst. Tetraploid blastocyst can be produced in vitro by electrofusion of 2-cell embryos. Objective: The aim of this study was to assess the effect of different voltages anddurations on fusion rate of bovine 2-cell embryos and their subsequent development in vitro. Material and Methods: The in vitro produced bovine 2-cell embryos were categorized into 3 groups: (1) fused group (FG); 2-cell embryos fused by exposure to differentvoltages (0.5, 0.75, 1, 1.25 and 1.5 kV/cm) and durations (20, 40, 60, 80 and 100 μs), (2) exposed control group (ECG); 2-cell embryos exposed to different voltages anddurations but remained unfused and (3) unexposed control group (UCG); embryoscultured without exposure to any voltage. The embryos from each group were cultured and fusion, cleavage and developmental rates were compared in each group.Results: The results show that increased voltage, increases the fusion rate up to 88% for 1.5 kV/cm; however, the rate of cleavage and blastocyst formation decreasessignificantly to 18% and 10% respectively (p<0.05). Increased duration does not significantly increase fusion rate, however, in high voltage, increased duration decreasescleavage rate and blastocyst formation rate. Blastocyst formation rate in UCG showed a better development (32%) compared to FG (20%) or ECG (22.5%) (p<0.05). Conclusion: It can be concluded that for optimal fusion, cleavage and development, one pulse of 0.75 kV/cm for 60μs should be applied.

Bovine, Embryo, Development, Electrofusion, Tetraploid