Objective: To observe the influence of isorhamnetin on cell cycle and cell apoptosis in H2O2-induced injury of human umbilical vein endothelial cells (HUVECs). Method :Cultured CRL-1730 cell was commonly incubated at 37 ℃ in 5%CO2 for 24 hours with isorhamnetin of different concentrations

then CRL-1730 was injured by H2O2 for 4 hours. Cell viability was measured by MTT assay. The rate of apoptosis and cell circles were detected by flow cytometry (FCM). Result : Iisorhamnetin could increase the cell viability in a concentration-dependent manner. Compared with the model group

the high dosage group showed A of 0.503 (increased 0.044)

with significant difference (P<0.01). Low dosage group was no significant difference

while the middle dosage group showed A of 0.48 (increased 0.027)

with significance (P<0.05). Isorhamnetin could decrease the cell apoptosis in a concentration-dependent manner

especially decrease the early apoptosis. Compared with the model group apoptosis rate of 77.78%

the apoptosis in high dosage group was 69.28% and the middle dosage group was 72.50%. Both had statistical significance (P<0.05). Isorhamnetin could inhibit the decrease in CRL-1730 caused by H2O2

showing by the cell cycle ratio of G0/G1. In the model group the ratio was 82.23%

in the high

middle and low dosage groups of isorhamnetin they were 69.43%

67.05% and 69.56% accordingly. All of them had significance. Isorhamnetin increased the percentage of cells in S phase and C2/M phase

the percentage of cells of S phase and C2/M phase of the model group was 11.77% and 1.91% respectively

while the high dosage was 23.39% and 7.18%

the middle dosage was 29.73% and 3.23%

and the low dosage was 27.42% and 3.01%. Conclusion : Isorhamnetin has protective effect on HUVECs injury induced by H2O2. The mechanism may be related to its antioxidant activity.