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The effects of uric acid supplementation during oocyte maturation on the in vitro fertilization of pigs
High incidences of polyspermic penetration in pig oocytes during in vitro fertilization (IVF) continue to challenge researchers. The objective of this study was to reduce the incidence of polyspermic penetration by supplementing uric acid during the later stages of oocyte maturation. Oocytes (n=160) were supplemented during the last 24 h of maturation with 0.02, 0.04, or 0.06 mM uric acid. The oocytes then experienced IVF and were evaluated for penetration, polyspermic penetration, and male pronuclear formation rates. The remaining embryos were evaluated for cleavage and blastocyst formation rates at 48 and 144 h after IVF, respectively. Supplementation of 0.04 and 0.06 mM uric acid were significantly toxic (P < 0.05) to the oocytes and removed from the remainder of the study. To determine the effects of uric acid supplementation on oocyte maturation, oocytes (n=135) were supplemented with 0.02 mM uric acid during the last 24 h of maturation and catalase and superoxide dismutase activities were determined. The remaining oocytes were analyzed for DNA fragmentation using an oocyte microgel electrophoresis assay. There were no significant differences between the 0.02 mM uric acid supplemented oocytes or those that were not supplemented with uric acid when comparing IVF kinetics, embryonic development rates, catalase activity, or DNA fragmentation. Oocytes supplemented with 0.02 mM uric acid has significantly higher (P < 0.05) levels of superoxide dismutase activity (5.81 ± 0.28 units/oocyte) compared to the oocytes not supplemented with 0.02 mM uric acid (1.26 ± 0.45 units/oocyte). These results indicate that supplementing 0.02 mM uric acid to pig oocytes during the later stages of maturation is not detrimental to fertilization or embryonic development success and increases the levels of superoxide dismutase activity in the maturing oocyte.
Keywords: polyspermy, oocytes, IVF