Objective   To study the reversal effect of tetrandrine (TET) on the multidrug resistance of Hep-2/ADM cell line and the possible mechanisms.     Methods   MTT method was used for the detection of the inhibitory effect of different concentrations of TET on the multidrug resistance of Hep-2/ADM cell line for selection of the non-toxicity concentration. MTT reduction assay was used to investigate the drug interaction of TET and vincristine (VCR) on HNE-1 (200) cell line. The reversal index (RI)

accumulation and excretion of drug

and the apoptosis of Hep-2/ADM cell line were detected by flow cytometry.     Results   No toxicity to Hep-2/ADM cell line was found when TET concentration was lower than 1.5 μg/ml. After interaction with TET (1.0 μg/ml and 1.5 μg/ml)

RIs of VCR on Hep-2/ADM were 1.72 and 2.00 folds

respectively. TET at the concentration of 1.5 μg/ml could increase the drug excretion and accumulation and also the apoptotic rate of VCR-induced Hep-2/ADM cell line.     Conclusion   TET can reverse the multidrug resistance of Hep-2/ADM cell line. The reversal effect may be related to the concentrations of TET. The possible mechanism may be that TET can increase the cell apoptosis of VCR-induced Hep-2/ADM cell line and can also increase the drug excretion and accumulation of the multidrug resistance cell line.