Objective To probe possible mechanisms of serum with Yinchen Wuling San（ 茵陈五 苓散） for regulating blood lipids

and to select the best concentration of the drug and action time. Methods 40 male SD rats were randomly divided into low

medium and high dose of Yinchen Wuling San groups

simvastatin group and blank group

with eight rats in each group. Low

medium and high dose of Yinchen Wuling San groups were respectively given 4 g /（ kg·d）

8 g /（ kg·d） and 16 g /（ kg·d） of Yinchen Wuling San. Simvastatin group was given 1 mg /（ kg·d） of simvastatin. Blank group was given 20 mg/（ kg·d） of saline lavage

2 times a day for three days to prepare medicated serum. LO2 cell lines in the logarithmic phase were incubated adherence for 24 h

then were randomly divided into low

medium and high dose of Yinchen Wuling San groups

simvastatin group and blank group

with 18 holes in each group. 10 μl of tested serum was added in each hole respectively. Each 18 holes with the same concentration were divided again into three groups

with 6 holes in each group

and cultivated for 24 h

48 h

and 72 h respectively. Real-time fluorescence quantitative method was used to detect expression levels of the low density lipoprotein receptor（ LDL-R） mRNA and 3-hydroxy-3-methylglutary-Co A（ HMG Co A） reductase mRNA in cells of each group. Results Compared with the blank group

expression of LDL-R mRNA significantly increased but expression of HMG-Co A reductase mRNA significantly decreased at each time point in each group with different doses of Yinchen Wuling San and the simvastatin group

（ P < 0. 05 or P < 0. 01）. And the expression of LDL-R mRNA reached the top point but the expression of HMG-Co A reductase mRNA was at the lowest point when medium concentration of Yinchen Wuling San intervened for 48 h. Conclusion Yinchen Wuling San can obviously raise LDL-R expression and lower HMG-Co A reductase expression. This may be its mechanisms of regulating blood lipids. The best effect can be obtained with the medium drug concentration and intervention for 48 h.