P-20: Determination of Effect of Melatonin on In vitro Maturation of Bovine Oocytes under Heat Stress

Background: Melatonin (N-acetyl-5-methoxytryptamine) is a multifunctional molecule that mediates several circadian and seasonal processes in animal reproduction. Melatonin and its metabolites are antioxidants and free radical scavengers. Furthermore, melatonin has been shown to act as an indirect antioxidant, and it is able to increase the activity of glutathione synthesis, and many others directly or indirectly implicated in the free radical removal. Melatonin can also diminish the activity or expression of enzymes or factors that are considered as prooxidants. So, the purpose of this study was to investigate the effect of melatonin supplementation during in vitro maturation (IVM) of bovine immature oocytes on nuclear maturation commercial tissue culture medium-199 (TCM-199) under Heat stress. Materials and Methods: Slaughterhouse derived bovine oocytes were cultured in four different conditions: IVM medium without melatonin at 38.5°C (control), IVM medium without melatonin at 41°C for first 12 hours (group 1), IVM medium supplemented with 10µM melatonin at 38.5°C (group 2), IVM medium supplemented with 10µM melatonin at 41°C for first 12 hours (group 3). IVM medium was TCM-199 supplemented with 10% Fetal calf serum (FCS), 0.5 µg/ml Follicle stimulating hormone (FSH), 5 µg/ml Luteinizing hormone (LH), 100 IU/ml penicillin and 100 µg/ml streptomycin. Results: Obtained results showed very significant differences (p<0.0001) between the all groups in reach to meiosis metaphase-II. After 24 hours of IVM, meiotic maturation rate in group supplemented with melatonin incubated at 38.5°C was significantly higher (p<0.0001) than without melatonin group (81% vs.70.67%) respectively. Also oocytes maturation rate in group supplemented with melatonin incubated at 41°C was very significantly different (p<0.0001) from group of without melatonin matured at 41°C (56.67% vs. 41.33%) respectively. Based on the results of this study, presence of melatonin in IVM medium provides positive effects on the maturation of bovine oocytes under heat stress. Therefore, the conclusions showed that adding melatonin improved the quality of IVM medium and increased the efficiency of maturation rate of bovine oocytes under heat stress. Conclusion: Obtained results showed very significant differences (p<0.0001) between the all groups in reach to meiosis metaphase-II. After 24h of IVM, meiotic maturation rate in group supplemented with melatonin incubated at 38.5°C was significantly higher (P<0.0001) than without melatonin group (81% vs.70.67%) respectively. Also oocytes maturation rate in group supplemented with melatonin incubated at 41°C was very significantly different (p<0.0001) from group of without melatonin matured at 41°C (56.67% vs. 41.33%) respectively. Based on the results of this study, presence of melatonin in IVM medium provides positive effects on the maturation of bovine oocytes under heat stress. Therefore, the conclusions showed that adding melatonin improved the quality of IVM medium and increased the efficiency of maturation rate of bovine oocytes under heat stress.