OBJECTIVE:To investigate the therapeutic mechanism of compound Yindan decoction(CYD)in a rat model of acute intrahepatic cholestatic(AIC).METHODS:A total of 108 adult male rats were randomly divided into control(n= 18)and AIC groups(n=90).AIC was induced in rats using alpha-naphthylisothiocyanate(ANIT)(75 mg/kg,10 mL/kg in corn oil,p.o.).Then,90 AIC rats were randomly divided into five groups:a control group(n = 18),a CYD high dose group(n = 18),a CYD middle dose group(n= 18),a CYD low dose group(n= 18),and a ursodeoxycholic acid(UDCA)group(n = 18).According to sampling time,each group was subdivided into three subgroups:24 h(n=6),48 h(n=6),and 72 h groups(n = 6).The CYD-high,-middle and-low groups were orally administered 24.48,12.24,and 6.12 g·kg~(-1)·d~(-1) modified CYD,respectively,while the model group was given 20 mL/kg of body weight of distilled water once a day.The UDCA group was given 67.5 mg·kg~(-1)·d~(-1) UDCA once a day.Radioimmunity assay was used to detect the activity of alanine aminotransferase(ALT),aspartate aminotransferase(AST),alkaline phosphatase(ALP),gamma-glutamyl transpeptidase(GGT)and the levels of total bilirubin(TBil)and indirect biliruin(DBil)in rats.Reverse transcription quantitative polymerase chain reaction(qRT-PCR),Western blot analysis,and immunohistochemistry were used to detect multidrug resistance-associated protein 2(MRP2)expression.In vitro,HepG2 hepatocellular carcinoma cells were treated with CYD medicated serum at a concentration of 15 mol/L.MRP2 and retinoid X receptor alpha(RXRa)expression was analyzed by qRT-PCR and Western blotting.RESULTS:Serum levels of ALT,AST,GGT,ALP,TBil,and DBil were significantly reduced in the CYD and positive drug groups compared with the control group(P