366 Bulletin UASVM Animal Science and Biotechnologies, 65(1-2)/2008 pISSN 1843-5262; eISSN 1843-536x THE EFFECT OF SEVERAL α-TOCOPHEROL CONCENTRATIONS ON SWINE OOCYTE MATURATION Miclea Ileana, M. Zăhan, Andrea Hettig, V. Miclea, I. Roman University of Agricultural Sciences and Veterinary Medicine, Faculty of Animal Science and Biotechnologies, 3-5 Manastur Street, 400372 Cluj-Napoca, Romania email: ileanamiclea@yahoo.com Key words: free radicals, swine oocytes, α-tocopherol Abstract. Free radicals play significant roles in the physiological processes happening in the ovary such as steroidogenesis, folliculogenesis, corpus luteum progesterone release and degeneration, and follicle rupture during ovulation. As defence, living systems employ antioxidants that they either produce or take up from the environment. Among these are ascorbic acid and α-topherol that have been shown to improve swine oocyte maturation and the development of bovine and swine embryos. The goal of this study was to establish the influence of several ascorbic acid and α-tocopherol concentrations on swine oocyte maturation in order to improve oocyte maturation media. Pig oocytes were cultured for 48 hours at 37°C in 5% CO 2 atmosphere, in M199 containing several α-tocopherol (5, 10, 20, 40 and 80 mM) concentrations. 48 hours after incubation cumulus expansion was assessed. The addition of 20 mM α-tocopherol to the maturation medium lead to a significant (p<0.05) increase in the number of matured oocytes. In conclusion swine oocyte maturation media can be improved by the addition of 20 mM α-tocopherol. INTRODUCTION The ambivalent relationship between living organisms and oxygen is a consequence of the fact that on one side it fuels aerobic life and on the other it is one of the main sources for the production of free radials. These are, according to the definition of Halliwell and Gutteridge (1989)”...any species capable of independent existence that contains one or more unpaired electrons”. They are produced by exogenous agents (radiation, heavy metals, pesticides) but also in the mitochondria, through the leakage of approximately 1%-2% of the electrons from the electron transfer chain (Boveris and Chance, 1973). Their formation is also guided by various enzymes such as cytochrome P450 mono-oxygenases (CYP450), NADPH- oxidase, xanthine-oxidase, ciclooxigenase, lipid oxygenase (Kovacic and Jacintho, 2001). In the cell, free radicals function as signal molecules by activating transcription factors and enzymatic reactions (Droge, 2002). In addition they play a significant role in steroidogenesis, follicle formation and progesterone release by the corpus luteum (Sawada and Carlson, 1996) and together with antioxidant enzymes bring about follicle wall rupture, ovulation (Fujii et al. 2005) and luteal regression (Agarwal et al., 2006). They are also involved in regulating embryo development and implantation (Guerin et al., 2001). Although cells have various antioxidant systems that should scavenge endogenous free radicals, their endogenous overproduction and the exogenous sources lead to an imbalance in redox metabolism and therefore to oxidative stress. It causes chain reactions that result in mitochondrial depolarization, cytochrome c release, lipid peroxidation, transcription factor activation and DNA damage leading to apoptotic and non-apoptotic cell death. As such, oxidative stress is increasingly recognized as a causative factor in the development of a