Abstract: Abstract：Objective To investigate the protective effects of folic acid on the oxidative damage that ox-LDL (oxi⁃ dized low-density lipoprotein receptor 1) render to human umbilical vein endothelial cells (HUVEC). Methods HUVECs were injured by ox-LDL (120 mg/L) for 24 h while they were incubated with various concentration of folic acid (0，15, 60, 150, 225, 300, 375 nmol/L). Then HUVECs were cultured in media contains same concentration of folic acid but without ox- LDL for 72 hours. Finally, HUVECs were harvested after 24, 48, 72 and 96 h. The morphological changes were observed us⁃ ing inverted microscope and cell viability were examined by MTT. Results Various concentrations of folic acid (0,15, 50, 100, 200 and 500 nmol/L) has no obvious promotion or inhibition effect in growth of normal HUVEC (P＞0.05). However, compared with the ox-FA-def group, 150, 225, 300 and 375 nmol/L of folic acid promoted proliferation of HUVECs with 96 and 120 hours of incubations (P < 0.05). Folic acid of 60, 150, 225, 300 and 375 nmol/L promoted the proliferation of HUVECs with 72 h and 96 hours of incubation (P < 0.05). Conclusion High dose folic acid can reduce the ox-LDL oxida⁃ tive damage on HUVEC in a concentration dependent manner.

Key words: folic acid, dose-response relationship, drug, endothelial cells, lipoproteins, LDL