Objective:To investigate the effect and mechanism of alcoholic extract of Pinellia ternate at non-cytotoxic concentration（inhibit rate≤5%）reversing the multidrug resistant（MDR） leukemia cell lines K562/A02.Method:Cells were seeded into 72-well plates at 2×108/L with varying concentrations（2.5

5

10

20

40 μg · L-1） of P.ternate for 72 h

MTT colorimetry was used to determine the cytotoxic effect of alcoholic extract of P.ternate and the sensibility to adriamycin of K562/A02 cell line.Flow cytometry was used to determine the expressive and functional changes of glycoprotein-170（p170）on the cell membrane dealed with alcoholic extract of P.ternate at non-cytotoxic concentration.And daunorubicin concentration in the cells was detected by flow cytometry.The statistical treatment with SPSS 16.0 was applied to deal with all the experimental data.Result:Alcoholic extract of P.ternate had definite cytotoxic effect on K562/A02

the non-cytotoxic dose of oxymatrine was 6.5 μg · L-1.Non-cytotoxic dose of alcoholic extract of P.ternate can significantly decrease the medium inhibition concentration（IC50） value of K562/ADM cell line to adriamycin（ADM）.The IC50was obviously reduced from（30.9±0.11） μg · L-1 to（10.1±0.21） μg · L-1

alcoholic extract of P.ternate at non-cytotoxic concentration could partly reverse MDR of K562/A02（3.06times）

and could descend the expression of p170 from 91.21% to 45.12%（P<0.01）.The exosmosis test of daunorubicin showed that intracellular concentration of chemotherapeutics concentration increased evidently.Conclusion:Alcoholic extract of P.ternate is able to partly reverse MDR of K562/A02 cell line could descend the expression of P170

and can restrain the function of pumping chemotherapeutics out of the cel1 and enhance the efficient intracellular concentration of chemotherapeutics which can kill leukemia cells of multidrug resistance

and partly reversed MDR of K562/A02.