Objective: To observe the effect of Longdan Xiegan pill (LD) on expression of multidrug resistance protein and neutrophil CD18 and tclarify the possible mechanism of LD to clear dampness-heat of liver and gallbladder. Method: Twenty healthy Wistar rats were randomly divided into 4 groups:control group

ANIT-treated model group

LD 5.0 g·kg-1group and LD 2.5 g·kg-1group. LD groups were administered orally for 8 days

while control group and model group were administered orally with equal distilled water

once daily. After the last administration for 1 h

model group and LD groups were treated with 100 mg·kg-1 ANIT

while control group was administered with equal peanut oil. After administration of ANIT 72 hours

The liver total RNA of all rats wwas extracted and the levels of MDR1a

MDR1b

MDR2

MRP1 and MRP2 mRNA in liver tissue were detected by reverse transcription polymerase chain reaction (RT-PCR). The expression of CD18 was measured by using flow cytometer. Total leukocytes and granular leukocytes were counted by using microcomputer controlled hematology analyzer. Result: The expression of MDR1a

MDR1b mRNA in model group wwas significantly higher than that of control group (P<0.05

P<0.01). The expression of MDR2

MRP1

MRP2 mRNA was not obviously changed. LD 5.0

2.5 g·kg-1 group had no obvious effects on expression of multidrug resistance protein in cholestatic rats. LD groups could reduce total leukocytes granular leukocytes and CD18 fluorescence intensity. Conclusion: LD has protection in ANIT-induced cholestatic rats

which is similar to the syndrome of dampness-heat of liver and gallbladder. The protection mechanism maybe mainly related to inhibiting endothelial-leukocyte adhesion

inhibiting inflammatory responses in bile ducts

alleviating biliary injuries

increasing bile flow of intrahepatic bile ducts

not related to the expresion of MRP1 and MRP2 mRNA in biliary epithelial cells.