Abstract： Objective To explore the expression and clinical significance of constitutive androstane receptor(CAR)in placenta syntrophoblast from patients with intrahepatic cholestasis of pregnancy(ICP).Methods Placenta were collected from women with ICP who delivered from April 2009 to March 2010 in First Affiliated Hospital of Chongqing Medical University.According to the severity of ICP,patients were classified into mild ICP group(n=10)and severe ICP group(n=10).Ten healthy pregnant women who delivered in the same period were chosen as control group.The location of CAR protein in placenta was studied by immunohistochemical streptavidin-biotin complex(SABC)method.CAR mRNA level was determined by reverse transcription(RT)-PCR technique and CAR protein expression level was determined by western blot.Results(1)CAR was located in the placenta syncytiotrophoblastic cells in control group and mild ICP group,showed light tan when stained,and was mainly in the cytoplasm.In severe ICP group,CAR was also located in placenta syncytiotrophoblastic cells but mainly in the nucleolus,showed dark tan when stained.(2)The mRNA expressions of CAR in control group,mild ICP group,severe ICP group were 0.06 ±0.03,0.07 ±0.03 and 0.56±0.03.respectively.CAR in severe ICP group was significantly higher than those in control group and mild ICP group(P＜0.05).The difference of mRNA between control group and mild ICP group wag not statistically significant(P＞0.05).(3)The CAR protein levels in control group,mild ICP group,severe ICP group were 0.74±0.03,0.79±01 03 and 1.02±0.04,respectively.CAR protein expression in the severe ICP group was significantly higher than the other two groups(P＜0.05).And there was no statistical significance between mild group and control group(P＞0.05).Conclusion In ICP women.especially severe ICP patients,the CAR expression in placenta syncytiotrophoblastic cells increased appreciably,which may be involved in the maintenance of placenta barrier function and protection in ICP pathogenesis.