Effect of different carboxylated poly l-lysine and dimethyl sulfoxide combinations on post thaw rabbit sperm...

Antifreeze proteins are biologically active substances which protect living organisms against freezing injuries. The effect of a synthetic antifreeze protein carboxylated poly l-lysine (CPLL) in the extender was evaluated in the presence of a conventional cryoprotective agent, dimethyl sulfoxide (Me₂SO), for freezing rabbit sperm cells. The experiment was conducted according to 2 × 3 factorial design including two Me₂SO (5 or 8%) and three CPLL (0, 0.5 or 1%) concentrations. CPLL supplementation improved post-thaw live and live-acrosome intact sperm rates (P<0.01) without a prominent influence on the motility (P>0.05) and live-membrane intact (P>0.05) sperm rates. The most striking effect of CPLL supplementation was seen on the DNA integrity where it reduced DNA fragmentation of sperm cells significantly by interacting Me₂SO (P < 0.01) during freezing and thawing. However, it could not replace Me₂SO in the extender and did not improve pregnancy rate. In conclusion, CPLL supplementation to the extender in the presence of Me₂SO improved sperm quality parameters and post-thaw DNA integrity.