Objective      To determine the expressions and the dynamic changes of Rho proteins (RhoA

RhoB and RhoC) and their kinase ROCK (ROCKⅠ and ROCKⅡ) in rat placenta at different stages of gestation.     Methods      A total of 20 pregnant female rats were randomly divided into 5 groups (n=4). Their placents were obtained when the rats were pregnant at 7

10

13

15

and 18 d respectively. Wet weight and diameter of the placenta were measured

and the number of the placenta was counted and recorded. The expression levels of RhoA

RhoB

RhoC

ROCKⅠ and ROCKⅡ were detected by immunohistochemical staining and Western blot analysis.     Results      With the increase of gestational period

the weight and diameter of the placenta were increased. The expression levels of RhoA and RhoC in 13

15

and 18 d of pregnant groups were significantly higher than those in 7 and 10 d of pregnant groups (P0.01)

but the expression of RhoB had no obvious difference among these groups (P0.05). ROCKⅠ and ROCKⅡ in 18 d of pregnant group was expressed significantly higher than those in 7

10

13 and 15 d of pregnant groups (P0.01).     Conclusion     The expression levels of RhoA

RhoC

ROCKⅠ and ROCKⅡ are increased in rat placental tissues with the elapse of pregnant period

but that of RhoB has no such significant change. These results indicate that Rho/ROCK signaling pathway may play an essential role in the development of placenta during normal pregnancy.