Effect of superoxide dismutase(SOD) on pronucleus formation of porcine oocytes fertilized in vitro

This study was undertaken to evaluate the effects of superoxide dismutase (SOD) on pronucleus formation in porcine oocytes fertilized in vitro by frozen-thawed spermatozoa. No differences were found in penetration rates when SOD was added to maturation or fertilization medium at any level tested in first and second experiments. Pronucleus formation rates were higher (P < 0.05) when SOD at 10 and 100 units was added to the maturation medium (46 and 53%, respectively) compared with the controls (26%). On the other hand, when the fertilization medium was supplemented with SOD at different concentrations (1, 10 and 100 units/ml), pronucleus formation rates (55, 52 and 50%) were significantly higher (P < 0.05) than in the control group. In third experiment, the oocytes were cultured in medium with (1 unit/ml) or without SOD for 8, 16, 24 and 32 h after insemination. The penetration rates had a tendency to increase as time of sperm-oocyte culture was prolonged. No significant differences, however, were observed in penetration rates between groups with and without SOD. On the other hand, the pronucleus formation rates were higher in medium with than without SOD at 8 (7 vs 0%), 16 (14 vs 3%), 24 (48 vs 16%; P < 0.01) and 32 h (49 vs 22%; P < 0.05). These findings demonstrate the advantage of culture with SOD on pronucleus formation in porcine oocytes penetrated by spermatozoa. However, SOD does not affect penetration rates and polyspermy.