Effect of DNA damage caused by cryopreservation of spermatozoa using a modified Single cell gell electrophoresis in the freshwater catfish Pangasianodon hypophthalmus(Fowler,1936)

Objective:To detect the integrity of sperm DNA in the catfish Pangasianodon hypophthalmus cryopreserved with Hanks balanced salt solution,5%-30%dimethyl acetamide(DMA)using the single-cell gel electrophoresis in order to test how sperm cryopreservation affected nuclear DNA stability.Methods:Electrophoresis was conducted for 60 min at 130 mA and 15 V.The comet images were analyzed using software CometScore 1.5,and parameters such as comet length,tail length and percentage DNA in the tail were obtained.Then the comet rate and damage coefficient were calculated.Results:There were no significant differences in motility,comet rate and damage coefficient between fresh sperm and cryopreserved sperm stored in 5%,10%,15%and 20%DMA,while the sperm cryopreserved with 25%and 30%DMA had lower motility,higher comet length and damage coefficients than those of fresh sperm.Conclusions:There was positive correlation between comet rate of cryopreserved sperm and the concentration of DMA.The toxicity of cryoprotectant is the main factor for DNA damage in cryopreserved sperm.