Toxic Effect of Paraquat on Sensitized V79 Cells Pretreated with 5-aza-2'-deoxycytidine

［Abstract］Objective　To study the effect of DNA methylation regulation on the toxic effect of paraquat on the sensitized V79 cells t pretreated with 5-aza-2'-deoxycytidine. Methods　V79 cells were treated by 5-aza-2'-deoxycytidine （5-Aza-2'-dc） for 12h， which is a DNA methylation inhibitor，and then treated with paraquat for 12h. The morphological changes of V79 cells were observed by microscopy and the cell viability was determined by MTT assay and trypan blue staining method．Results Microscopic examination showed that the combination of 5-Aza-2'-dc and paraquat had stronger effect in inhibiting the growth of V79 cells(the cells became smaller and poorer adhensive ability ) than single 5-Aza-2'-dc or paraquat. MTT assay showed that cell viability in the combination group （54.47±3.04）% was significantly lower than the 5-Aza-2'-dc group（95.52 ± 0.90）% and paraquat group（89.68±4.26）% （P＜0.05）. Trypan blue staining assay showed that the death rate of cells in the combination group（53.58±1.57）% was significantly higher than the 5-Aza-2'-dc group（7.44 ± 2.31）% and paraquat group（12.90±1.21）%（P＜0.05）. Conclusion　5-Aza-2'-dc promotes V79 cells damage caused by paraquat.