Effects of follicle diameter on early embryonic development and oxidative stress in bovine oocytes
In order to explore the effects of follicle diameter on early embryonic development and oxidative stress in bovine oocytes,in the experiment,follicles were isolated from fresh healthy bovine ovaries,and the follicles were divided into larger follicle group(L group,5 mm≤follicle diameter<10 mm)and smaller follicle group(S group,1.8 mm≤follicle diameter<5 mm)according to their diameters.Cumulus-oocyte complexes(COCs)were isolated from different groups of follicles and graded;the effects of different follicle diameters on oocyte maturation rate,cleavage rate,and reactive oxygen species(ROS),glutathione(GSH)levels,antioxidant genes(SOD1,SOD3,SRIT2 and GPX1)expressions in oocytes at GV and MⅡ stages were analyzed.The results showed that COCs were divided into five grades:A,B,C,D,and E,and there was no significant difference in the ratio of COCs between group L and group S(P>0.05).There was no significant difference in oocyte maturation rate between group L and group S(P>0.05),and the cleavage rate of oocytes in group L was significantly higher than that in group S(P<0.05),which were 62.67%and 50.67%,respectively.In the GV stage of oocytes,the level of ROS of oocytes in group L was significantly lower than that in group S(P<0.05),and the level of GSH was significantly higher than that in group S(P<0.05).In the MⅡstage,the ROS level of oocytes in group L was significantly higher than that in group S(P<0.05),and the level of GSH was significantly lower than that in group S(P<0.05).The mRNA relative expression levels of SOD1,SOD3,SIRT2 and GPX1 genes in group L were significantly higher than those in group S(P<0.05)at GV and MⅡ stages of oocytes.These results indicated that oocytes in larger follicles had better antioxidant properties and developmental potential.
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