184 Effects of cyanidin supplementation on in vitro maturation of pig oocytes

Abstract

Oxidative stress can have a negative effect on oocyte maturation during in vitro production of pig embryos. Imbalance of reactive oxygen species and antioxidant levels can affect the progression of oocyte maturation up to the point of fertilization. Antioxidants are effective in maintaining more ideal reactive oxygen species levels, which help to protect oocytes from potential harmful effects of oxidative stress. Berries from the elder plant (Sambucus sp.) contain high levels of a broad spectrum of antioxidants. One of these antioxidants, cyanidin, when supplemented to maturation medium at 100 μM concentrations, reduces reactive oxygen species formation and improves IVF and early embryonic development in pigs. However, changes in the enzyme mechanisms of action during oocyte maturation due to cyanidin supplementation are unknown. Therefore, the objective of this study was to characterise the intracellular oocyte enzyme mechanisms between oocytes supplemented with 100 μM cyanidin during 40 to 44 h of maturation (n = 600) and oocytes without supplementation of cyanidin during maturation (n = 558). At the end of maturation, oocytes were evaluated for either glutathione peroxidase (n = 300), catalase (n = 564), or superoxide dismutase (n = 294) activities. Glutathione peroxidase activity was determined by following the rate of NADPH oxidation, catalase activity was determined by following the rate of hydrogen peroxide decomposition, and superoxide dismutase activity was determined by following the reduction rate of cytochrome c, utilising the xanthine-xanthine oxidase system. Data were analysed using ANOVA and Tukey's test. There were no significant differences between oocytes matured with 100 μM cyanidin and those that were not when comparing glutathione peroxidase and superoxide dismutase activities. Supplementation of 100 μM cyanidin to maturation medium increased (P < 0.05) catalase activity in oocytes (0.78 ± 0.15 units/oocyte) compared with no cyanidin supplementation (0.14 ± 0.11 units/oocyte). These results indicate that supplementing 100 μM cyanidin to the maturation medium of pig oocytes could reduce the negative effects of oxidative stress by increasing intracellular catalase activity during oocyte maturation.