Abstract: Objective To determine the expression of RhoA/Rho-kinase in the vaginal smooth muscle cells of castrated rats and the effect of estrogen on the expression of RhoA/Rho-kinase. Methods 30 female SD rats of 10 weeks were randomly divided into groups C4(4-week control group),C6(6-week control group),OE4(4-week bilateral ovariectomy),OE6(6-week bilateral ovariectomy),E4(4-week bilateral ovariectomy and oestrogen replacement) and E6(6-week bilateral ovariectomy and oestrogen replacement). 4 and 6 weeks after surgery, the serum estradiol level was determined and the expressions of Rock1 and Rock2 in the vaginal smooth muscle were detected by western blot.　Results Serum estradiol was significantly lower in group OE4 and OE6 than in groups C4 and C6( P < 0. 01) .RhoA/Rho-kinase was expressed in the vaginal smooth muscle cells of the rats. The protein expression of Rock1 was significantly more in groups OE4 and OE6 than in groups C4 and C6(0.261±0.039 vs 0.207±0.032；0.270±0.037 vs 0.208±0.032，P＜0.05), and so were Rock2 in groups OE4 and OE6 in comparison with groups C6 and E6(0.377±0.035 vs 0.294±0.033；0.388±0.038 vs 0.300±0.034，P＜0.05). Conclusion The replacement of oestrogen may inhibits the expression of RhoA/Rho-kinase in the vaginal smooth muscle cells of the rats,E2 may regulate the function of vaginal smooth muscle through regulate the expression of RhoA/Rho-kinase.

Key words: Key words: RhoA/Rho-kinase, estrogen, vaginal, smooth muscle