Objective:To discuss the role of serum and glucocorticoid-induced protein kinase 3(SGK3)in the resumption of the first meiotic division in the oocytes of the mice,and to preliminarily clarify the regulatory mechanism of SGK3 in the early development of mammalian oocytes.Methods:The germinal vesicle(GV)stage mouse oocytes were obtained by superovulation techniques.The SGK3 mRNA,obtained from in vitro transcription of expression plasmids,was injected into the GV stage oocytes by microinjection techniques.The oocytes were divided into control group,Tris-EDTA buffer(TE)group,and SGK3 mRNA group.Western blotting method was used to detect the expression levels of SGK3 protein in the oocytes in various groups;the germinal vesicle breakdown(GVBD)rates of the oocytes in various groups were observed and calculated at 1,2,3,and 4 h after microinjection of SGK3 mRNA;the morphological appearance of the oocytes in various groups was observed by SGK3 antibody dilution inhibition experiment;Western blotting method was used to detect the expression levels of phosphorylated SGK3(pSer48)(SGK3-pSer48)and phosphorylated cell division cycle protein 2(CDC2)(pTyr15)(CDC2-pTyr15)proteins in the oocytes cultured in vitro at different time points.Results:Compared with control group and TE group,the expression level of SGK3 protein in the oocytes in SGK3 mRNA group was increased(P＜0.01),and the GVBD rates at 1 and 2 h after microinjection were increased(P＜0.01).The SGK3 antibody dilution inhibition experiment results showed that as the increasing of concentration of SGK3 antibody,the GVBD rates of the oocytes in various groups were decreased in a concentration-dependent manner.After overexpressing SGK3,compared with control group,the time when CDC2-pTyr15 protein expression could not be detected in the oocytes in SGK3 mRNA group was advanced by at least 1 h.After treated with different concentrations of SGK3 antibody,compared with control group,as the increasing of concentration of SGK3 antibody and the extending of treatment time,the expression level of CDC2-pTyr15 protein in the oocytes was gradually decreased(P＜0.01),and the expression level of SGK3-pSer486 protein was gradually increased(P＜0.01).Conclusion:Over-expression of SGK3 can increase the GVBD rate of oocytes of the mice and accelerate the dephosphorylation of CDC2-pTyr15,while the dephosphorylation of CDC2-pTyr15 is later than the phosphorylation of SGK3-Ser486.SGK3 likely serves as an upstream regulator of CDC2 and participates in controlling the resumption of the first meiotic division in the oocytes of the mice.