P Sedaghat - Department of Animal Sciences, College of Agriculture, Zanjan University, Zanjan, Iran. Department of Embryology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR,Tehran, Iran
R Masoumi - Department of Animal Sciences, College of Agriculture, Zanjan University, Zanjan, Iran
M Sharafi - Department of Embryology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR,Tehran, Iran
B Rostami - Department of Animal Sciences, College of Agriculture, Zanjan University, Zanjan, Iran

Background: Cryopreservation of bull sperm associated with an increase in reactive oxygen species (ROS) which lead to in-duce lipid peroxidation of sperm membrane. During the freeze-thaw process, the sperm is subjected to biochemical, osmotic, physical stress in which fertility potential of thawed semen is reduced. Mitochondria is known to be an important organelle of sperm that regulates the antioxidant response during cryo-preservation. The Mitochondria Uncoupling protein (UCP2) is a key protein that regulates the antioxidant activates of sperm in freeze-thaw process. The purpose of this study was to evalu-ate the effects of cryopreservation on the UCP2 protein of bull sperm and it’s associated with antioxidant systems, motility, mitochondria activity, apoptosis status and ROS concentration. Materials and Methods: Bull semen was diluted in extenders containing different concentrations of Xanthine Oxidase (XO) as activator of XO and then cryopreserved. Several quality in-dicators of sperm were compared in cryopreserved semen in different rather than fresh semen.Results: The results showed that UCP2, membrane potential, viability, motility and membrane integrity were negatively af-fected by the cryopreservation (P<0.05). The reactive oxygen species (ROS) and lipid peroxidation and were significantly after cryopreservation (P<0.05). Sublethal concentration of Xanthine Oxidase (XO) increased the several quality indicators of thawed semen (P<0.01). Also, XO improved the membrane integrity and motility of sperm after cryopreservation (P<0.05). Conclusion: It can be concluded that due to freezing process, UCP2 reduced post cryopreservation that may be responsible for the lower antioxidant systems and consequently lower qual-ity of sperm post-thawing. Sublethal concentration of XO can partially restore these negative impacts.

Apoptosis, Artificial Insemination, Semen