P-90: Ascorbic Acid Effects on In Vitro Fertilization of Ovine Oocyte with or without Cumulus Cells

Background: In vitro maturation and fertilization are techniques to increase efficiency of mammals reproduction. However, in vitro culture conditions exert an imbalance between oxidants and antioxidants which may reduce live birth and pregnancy rates when compare to in vivo conditions. Materials and Methods: The present study was conducted as a part of the ovine IVF program organized by University of Tehran, Department of Animal Science between the 16th April and the 24th of June (Spring), 2012. About 250 ovaries were obtained at a local abattoir in Karaj city, Iran, from the slaughtered animals. Ovarian follicles, 2-6 mm in diameter were aspirated and collected ina pre-incubated Hepes-modified TCM199 medium. The oocytes were allocated to 2 groups, cumulus-oocyte complexes (COCs) and denuded oocytes (DOs). Each 20 oocytes were cultured in a drop of IVM medium (200 _mL) and different levels of ascorbicacid (0, 150, 250 and 300 μM), covered with mineral oil for 24 hours, at 37.5°C in 5% CO2 in air and 85% humidity. mature oocytes were washed three times in IVF medium. Thereafter, 20 matured oocytes were transferred to 200 ml of the already incubated IVF medium droplets. Then, sperm suspension was finally added to the each fertilization drop to obtain a final concentration of ≈1×106 sperm/ ml. The gametes were cultured under mineral oil for 18 hours at 38.5°C in 5% CO2 humidified air. Results: Interestingly, the fertilization rate of denuded oocytes that 250 and 300 μM ascorbic acid concentrations supplemented to their maturation culture medium was significantly lower than cumulus-oocyte complex group (p<0.05). Conclusion: This may express the pro-oxidant effects of high concentrations of ascorbic acid on ovine oocytes fertilization.