Influence of Alpha-Tocopherol and Ascorbic Acid on Swine Oocyte Viability and Maturation

Abstract

As defense against oxidative stress, living systems employ antioxidants that they either produce or take up from the environment. Among these ?-tocopherol and ascorbic acid are some of the most important and have been shown to protect cell components against oxidation. The goal of this research was to establish whether supplementation with ?-tocopherol or/and ascorbic acid could improve viability and maturation of porcine oocytes. Pig oocytes were cultured for 44-45 hours at 37°C in 5% CO2 atmosphere in M199 containing 20 ?M ?-tocopherol or/and 750 ?M ascorbic acid. Afterwards, cumulus oophorus expansion was assessed and oocytes were denuded. Viability and the presence of the first polar body were assessed by fluorescent staining with 3’, 6’ fluorescein diacetate and Hoechst 33258. Differences between treatments were analyzed by the analysis of variance and interpreted using the LSD test. Supplementation with 750 ?M ascorbic acid and the combination of ?- tocopherol and ascorbic acid resulted in significantly greater (p<0.05) percentages of COCs that were scored as 3. Overall, cumulus expansion was promoted by the 750 ?M ascorbic acid treatment. The percentages of oocytes with a visible first polar body were highest when ascorbic acid and the antioxidant mix were added to the maturation media. However, these supplementations had a negative effect on oocyte viability. This was maximal if 20 ?M ?-tocopherol was present the medium. The research indicates that 20 ?M ?-tocopherol has a positive influence on preserving oocyte viability while 750 ?M ascorbic acid and the antioxidant combination promote cumulus oophorus expansion and the formation of the first polar body.