Abstract: Objective To study the roles of MDR1 and MRP1 gene in acquired a rsenic tolerance in chronic a rsenic-exposed(CAsE)cells for a rsenic-resistance gene research.Methods The roles of MDR1 and MRP1 were inhibited with inhibitor Verap ami MK571 on single and combined level,respectively.MTT was used to detect the survival rates and IC₅₀ of cells in test and control groups.AFS was used to detect a rsenic with in the CAsE cells at different times.Results For different a rsenic concentrations(2,4,8,16,32,64μmol/L),the survival rates of cells with the inhibitor was 73.5±0.02,54.6±0.07,44.2±0.05,20.5±0.09,13.5±0.1,7.6±0.05%,which were obviously lower than that of control groups(93.5±0.05,71.5±0.02,49.2±0.03,38.8±0.08,37.6±0.06,19.5±0.04%).With the role of Verapamil,MK571,the IC₅₀ value was 8.8 and 6.22μmol/L,respectively.Meanwhile the two inhibitors combined plays an obviously reverse role,and the IC₅₀ was 5.23μmol/L.The arsenic content in the CAsE cells with the role of MK571 was obviously higher than that in control and Verapamil groups and achieved the max imum value of 1.62ng at 10 hours after the treatment with statistically significant difference(P<0.05).Conclusion MDR1 and MRP1 plays an important role in the process of CAsE cells acquired to lerance to acute a rsenic exposure.