Alpha-tocopherol and Ascorbic Acid Combinations Influence the Maturation of Sheep Oocytes

Abstract

The goal of this research was to establish whether supplementation with combinations of α-tocopherol and ascorbic acid could improve the maturation and expansion of sheep cumulus-oocyte complexes. Sheep oocytes were cultured for 24 hours at 37°C in 5.4% CO2 atmosphere in M199 containing 20 µM α-tocopherol+750 µM ascorbic acid or 5 µM α-tocopherol+250 µM ascorbic acid. Afterwards, cumulus oophorus expansion was assessed and oocytes were denuded. The presence of the first polar body was assessed by fluorescent staining with Hoechst 33258. Differences between treatments were analyzed by the analysis of variance and interpreted using the LSD test. Supplementation with the combination of 20 µM α-tocopherol+750 µM ascorbic acid resulted in significantly greater (p<0.05) percentages of COCs that were scored as 3. However, the number of COCs scored at 4 decreased. The same dynamic could be seen when oocytes were checked for the presence of the first polar body. Percentages decreased with the increase in antioxidant concentration. This indicates that although antioxidants, in these particular concentrations have been proven to have a positive influence on swine oocyte maturation the same cannot be said for ovine female gametes.

Keywords

• α-tocopherol
• ascorbic acid
• maturation
• oocyte
• sheep