·AIM:To investigate the effects of suramin combined with dexamethasone on proliferation of cultured pig retinal pigment epithelial(RPE)cells.·METHODS:Cultured RPE cells were treated with different concentrations of suramin(0.05,0.1,0.2,0.4g/L)lonely and combined with 0.2g/L dexamethasone for 4 days.The inhibition ratio of RPE cells was measured by tetrazolium(MTT)colorimetric assay.0.2g/L suramin and 0.2g/L dexamethasone were added to RPE cells respectively,flow cytometry(FCM)analysis was used to examine RPE cells cycles.The ultrastructure of cells treated whit 0.2g/L suramin,0.2g/L suramin combined with 0.2g/L dexamethasone and 0.4g/L suramin were observed by transmission electronic microscopy(TEM).·RESULTS:Suramin could inhibit the proliferation of RPE cells in a dose-dependent manner.The inhibition ratios of RPE cells treated with suramin combined with 0.2g/L dexamethasone(42.3%,52.1%,65.6%,78.8%)were much higher than those treated with suramin(16.0%,27.3%,40.5%,64.1%).FCM revealed that the cells were blocked in G2/M phase in their cell cycle by suramin(P<0.01)and blocked in G2/M phase by dexamethasone(P<0.01).The ultrastructure of cells were well at the concentrations of 0.2g/L suramin and 0.2g/L suramin combined with 0.2g/L dexamethasone,but at the concentration of 0.4g/L,significant reduction of microvilli and crenulation of cell nucleus were observed.CONCLUSION:Suramin combined with dexamethasone can effectively inhibit RPE cells growth in vitro