Abstract: AIM: To investigate the protective effects of 3, 4, 5, 6-tetrahydroxanthone on damages of endothelium- dependent relaxation induced by high glucose. METHODS: The aortic rings obtained from the rats were exposed to high glucose (25 mmol°L^-1) for 24 h or endothelial cells were incubated with high glucose (30 mmol°L^-1) for 48 h, respectively.Endothelium-dependent relaxation was measured.Activity of lactate dehydrogenase (LDH), contents of malondialdehyde (MDA) and nitric oxide (NO) in the medium were measured.RESULTS: Exposure of aorta rings to high glucose (25 mmol°L^-1) for 24 h caused a marked decrease in endotheliun- dependent relaxation.Pretreatment with 3, 4, 5, 6- tetrahydroxyxanthone (1, 3 or 10 μmol°L^-1) or probucol (10 μmol°L^-1) significantly improved endothelium-dependent relaxation in a dose-dependent manner.The release of LDH, the contents of MDA and NO in the medium marked increased after exposure of HUVEC to high glucose (30mmol°L^-1) for 48 h.Pretreatment with 3, 4, 5, 6-tetrahydroxyxanthone (1, 3 or 10 μmol°L^-1) or probucol (10 μmol°L^-1) significantly decreased the increased release of LDH, the increased content of NO and MDA in the medium.CONCLUSION: 3, 4, 5, 6-tetrahydroxanthone may preserve endothelial dysfunction induced by high glucose, and the protective effects of 3, 4, 5, 6-tetrahydroxanthone may be related to reduction of endothelial cells damages by inhibiting lipid peroxidation.

Key words: 3,4,5,6-tetrahydroxanthone, high glucose, endothelium, lipid peroxidation