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The effects of glucuronic acid and N-acetyl-D-glucosamine on the in vitro fertilization of pigs
High incidences of polyspermic penetration in porcine 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 glucuronic acid (GA) and N-acetyl-D-glucosamine (GlcNAc) during maturation of the oocytes. Oocytes (n=1000) were supplemented during the last 24 h of maturation with either 0.01 mM GA, 0.01 mM GlcNAc, 0.01 mM GA and GlcNAc, or 0.005 mM GA and GlcNAc and then evaluated for perivitelline space thickness. Using a portion of the oocytes (n=330), intracellular glutathione (GSH) concentrations were determined after maturation. The remaining oocytes were fertilized and either evaluated 12 h after IVF for cortical granule release and fertilization kinetics or they were cultured as embryos. The PVS thickness was significantly thicker (P < 0.05) in all treatments compared to the control (4.45 ± 0.71 μm). Oocytes supplemented with 0.01 mM GA had significantly lower (P < 0.05) intracellular GSH concentrations (4.16 ± 0.13 pmol/oocyte) compared to oocytes without supplementation (5.86 ± 0.09 pmol/oocyte). Oocytes supplemented with 0.005 mM GA and GlcNAc had significantly higher (P < 0.05) intracellular GSH concentrations (11.79 ± 2.06 pmol/oocyte) compared to oocytes that were not supplemented. Oocytes supplemented with 0.01 mM GA or 0.01 mM GA and GlcNAc had significantly more cortical granule exocytosis (P < 0.05) compared to the other treatments. Oocytes supplemented with GA had significantly lower incidences (P < 0.05) of polyspermic penetration compared to the control (32.00 ± 4.80%) or 0.01 mM GlcNAc (40.00 ± 7.93%) and significantly higher rates (P < 0.05) of cleavage and blastocyst formation by 48 and 144 h post-fertilization. These results indicate that supplementing GA during oocyte maturation decreases the incidence of polyspermic penetration by increasing PVS thickness and cortical granule exocytosis in pigs.
Keywords: glutathione, polyspermic penetration, oocyte penetration