ABSTRACT
<p><b>OBJECTIVE</b>To investigate the mechanism of multidrug resistance (MDR) in a human glioma cell and methods for overcoming multi-drug resistance.</p><p><b>METHODS</b>MDR cell line C(6)/adr was established. The expression of the mdr-1 gene and its P-glycoprotein (P-gp) in the C(6)/adr cell line was observed by RT-PCR and flow cytometry. The reversal of MDR by verapamil, erythromycin, dihydropyridine, P-gp monoclonal antibody and Salvia miltiorrhiza (SM) was studied by microtiter tetrazolium (MTT) assay or by high performance liquid chromatographic assay.</p><p><b>RESULTS</b>The mdr-1 gene of the C(6)/adr cell line was positive, over-expressing P-gp. The drug-resistance of the C(6)/adr cell lines could be partly reversed by 2 - 6 microg/ml of verapamil, 50 - 100 microg/ml of erythromycin, or 5 microg/ml of dihydropyridine. As concentration increased, they had a better effect. Among these drugs, 100 microg/ml of erythromycin had the best result of reversal. Dihydropyridine 1 microg/ml, P-gp monoclonal antibody and SM had no effect.</p><p><b>CONCLUSION</b>The mdr-1 gene and its expression might be associated with the MDR of glioma cells. Verapamil, erythromycin and dihydropyridine could reverse the MDR of glioma cells.</p>