Effect Of Follicle Diameter On Oxidative Stress In Bovine Oocyte And Early Embryos

In mammalian ovaries,there are a significant number of follicles in different stages of follicular development.Due to the different diameters of follicles,the antioxidant system in the oocytes may have different effects on the developmently potential of oocytes in vitro.By the bovine ovaries for experimental samples of this study,the follicles was grouped according to the different diameters about the Small groups of 1.8-5 mm and the Large group of 5-10 mm,get the bovine cumulus oocyte complexes(COCs)from the follicle,and grade them according to the COCs rating.Through in vitro culture,detection the main detection indicators about GV stage,MII stage and 8-cell stage,which was the development ability after fertilization of oocytes,ROS level,GSH level and mitochondrial membrane potential level,and the m RNA expression about anti-oxidation-related gene.To study the effects of follicle diameter on oxidative stress in bovine oocytes and early embryos.The experimental results are as follows:1.The influence of follicle diameter on the improvement of bovine oocytes:oocytes were divided into groups according to different diameters,moreover it were extracted and cultured in vitro for the MII stage and 8-cell stage.The study was proved that there was no difference in maturation rate between the Large group and the Small group(P> 0.05);The mitosis rate and 8-cell rate in the Large group were hugely higher than those in the Small group(P< 0.05).2.The effect of follicle diameter on the oxidative stress of bovine oocytes:(1)The oocytes at GV stage and MII stage from the Large and Small groups,and ROS,GSH and Δ Ψ m levels were detected respectively.At GV stage,ROS level in the Large group was lower than that in the Small group(P< 0.05);GSH level was higher than that in Small group(P< 0.05);ΔΨ M was lower than Small group(P<0.05).At MII stage,ROS level in the Large group was higher than that in the Small group(P< 0.05);GSH level was lower than that in Small group(P<0.05);ΔΨ M was lower than Small group(P< 0.05).(2)To detect the m RNA about the genes(SOD1,SOD3,SIRT2,GPX1)about anti-oxidation with qRT-PCR in the Large and Small groups when oocytes at GV stage and MII stage.The levels of either m RNA in the Large group was higher than the Small group(P< 0.05).3.The influence of follicle diameter on the oxidative stress of bovine early embryo:(1)The COCs from the Large and Small groups were used to cultured in vitro to the 8-cell stage,and detected respectively ROS,GSH and JC-1 levels.ROS levels in the Large group were higher extremely(P<0.05);GSH levels was higher extremely(P<0.05);Δ Ψ m was higher than Small groups extremely(P<0.05).(2)The m RNA of anti-oxidation related genes(SOD1,SOD3,SIRT2,GPX1)were detected with the qRT-PCR in the Large and Small groups when oocytes were cultured in vitro to the 8-cell stage.The levels of each m RNA in the Large group were higher than the Small group significantly(P<0.05).The results showed that oocytes in the large follicle group had higher developmental potential,and during the GV stage,oocytes in the large group were relatively less exposed to oxidative stress;during the MII stage,oocytes in the large group were more sensitive to changes in external oxygen concentration during in vitro culture;during the 8-cell stage,oocytes in the Large group had stronger reducing ability and more stable mitochondrial state.