Objective:To explore the mRNA expression of INSL3 gene in perinatal mice Leydig cells exposed to diethylstilbestrol(DES) in vivo and in vitro.Methods:The Leydig cells were isolated from fetal mouse testis and were cultured in DMEM/F12 medium and identified by 3 beta-hydroxysteroid dehydrogenase(3β-HSD).Reverse transcriptase-polymerase chain reaction(RT-PCR)and in situ hybridization were used for examination of the expression levels of INSL3 mRNA in primarily cultured Leydig cells incubated with DES(at the dose of 1μg/L

5μg/L and 25μg/L

respectively).Pregnant mice were exposed to DES at the dose of 1

10 or 100μg/kg body weight per day by gavage from gestation day(GD)12 to postnatal day(PND)3.The expression of INSL3 gene in neonatal mouse testis was investigated by RT-PCR.Results:Histological alterations of primarily cultured Leydig cells and neonatal mouse testis exposed to DES were observed.The expression level of INSL3 mRNA in DES treated groups including the primarily cultured Leydig cells and male mouse offspring’s testis were lower than those of the control groups.Conclusion:DES can downregulate the expression level of INSL3 mRNA in Leydig cells in vitro and in vivo.It may be a possible mechanism that DES interferes with gubernaculum development and cause cryptorchidism.