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

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.