Abstract:Objective:To explore the mechanism of reversal of mutidrug resistance of GBC-SD cell lines by grape seed polyphenols（GSP）. Methods:GBC-SD cell lines were used to determine the effect of GSP. MTT assay was adopted to evaluate the cytotoxity(IC50), RT-PCR were used to determine MDR1 mRNA, P- gp,bcl-2 and cellular adriamycin was measured by flow cytometry. Results:In non-toxic(3μg/mL) and low toxic(6μg/mL) comcentration of GSP treated group(P<0.05), the IC50 of chemotherapeutic agents was reduced the expression of P-gp,bcl-2 and MDR1 mRNA inhibited(P<0.05), and cellular accumulation of adriamycin increased(P<0.05). Conclusions:GSP could reverse mutidrug resistance of GBC-SD cell lines, and the suggested mechanism is that GSP decreased the expression of P-gp,bcl-2 and MDR1 mRNA.