s Kazemi Noureini - Dept. Biology, Faculty of Science, Hakim Sabzevari University, Sabzevar, Iran
z Jarrahifar - Dept. Biology, Faculty of Science, Hakim Sabzevari University, Sabzevar, Iran

Multidrug resistance (MDR) can limit efficacy of chemotherapy. The best studied mechanism involves P-gp (P-glycoprotein) that pumps anti-cancer drugs out of tumor cells. Therefore a new tentative strategy aims to find compounds that can reverse MDR. Several natural products are known to at least partially overcome P-gp mediated MDR. Here we evaluated the inhibitory potencies of some benzylisoquinloine alkaloids on P-glycoprotein activity. Rhodamine 123 accumulation assay was employed for P -gp dependant efflux in presence of each compound. Rhodamine123 is a fluorescent substrate of P-glycoprotein, which is readily effluxed in MDR -overexpressing cancer cells. This study focuses on screening this class of alkaloids because of their known antiproliefrative effects of several of the members. The goal is finding those which potently interfere with P-gp in drug resistant cell line such as MCF7-ADR in comparison with the sensitive parental cell line MCF7. The accumulation of rhodamine 123 was measured in both cell lines that were pre -incubated with different concentrations of each compound for 48 h and in MCF7-ADR cells in presence of the anticancer drug doxorubicin. Then 1 μg/ml rhodamine 123 had been added and incubated for 4 hours. The fluorescence of Rho123 was measured in cell lysates and data were compared with samples treated with verapamil was a positive control. Accumulation of rhodamine 123 in MCF7/ADR cells in the presence of various concentrations of alkaloids increased in various levels, and more or less in a concentration dependent manner in comparison with untreated samples. The present results indicate that some of this family of alkaloids may provide useful candidates for further studies combating drug resistance.

drug resistance, P-glycoprotein, rhodamine 123, natural alkaloids