Objective:To investigate the effect of hyperglycemia on the apoptosis and proliferation of islet endothelial cell line MS-1. Methods: MS-1 cells were treated with different concentrations of glucose (5.6,25.0 and 33.6 mmol/L) for different time (12 or 24 h). The apoptotic cells were detected by flow cytometry,and the cell proliferation was tested using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay. The expressions of GRP78,CHOP,caspase-3,caspase-12 mRNA were examined by reverse transcription and polymerase chain reaction(RT-PCR),and the expressions of GRP78,CHOP protein were examined by Western blot. Results: After treated with glucose for 12 h or 24 h,the apoptotic rates were obviously higher in 25.0 and 33.6 mmol/L group than in 5.6 mmol/L group(P < 0.05),while the cell proliferation was significantly lower in 25.0 and 33.6 mmol/L glucose treated group than that in 5.6 mmol/L glucose treated group(P < 0.05). The mRNA levels of CHOP,caspase-3,caspase-12 and the protein level of CHOP increased in a dose-dependent manner after treated with glucose(P < 0.05);while the mRNA and protein levels of GRP78 increased after treated for 12 h,and decreased at 24 h(P < 0.05). Conclusion: Hyperglycemia significantly promotes apoptosis and decreases proliferation of MS-1 cells,the mechanism may account for endoplasmic reticulum stress.