Abstract: BACKGROUND AND AIM: Effects of quercetin on expressions of mdr1 gene and P-glycoprotein in B-MD-C1(ADR＋/＋) cell line were studied in vitro. MATERIALS AND METHODS: After treatment with or without various concentrations of quercetin (10, 20, 40 μmol/L) for 48 h, the expression in mdr1 gene in B-MD-C1(ADR＋/＋) cell was detected by RT- PCR and expression of P-gp protein with IHC. The chemosensibility of B-MD-C1(ADR＋/＋) cells was evaluated by means of MTT. Changes of subcellular distribution of ADM in B-MD-C1(ADR＋/＋) cell was examined by confocal scanning laser microscopy (CSLM). RESULTS: After treatment with different concentrations of quercetin (10, 20, 40 μmol/L) for 48 h, the expression levels of mdr1 gene and P-glycoprotein in B-MD-C1(ADR＋/＋) cells were decreased significantly(P<0.05). The abnormal distribution of ADM in B-MD-C1(ADR＋/＋) cells was restored. CONCLUSION: Quercetin could reverse the multidrug resistance by down-regulating the expression of mdr1 gene and P-glycoprotein and restoring the distribution of ADM in B-MD-C1 (ADR＋/＋) cells.

Key words: uercetin, multidrug resistance, mdr1, P-glycoprotein