Mechanism of quercetin for protection of endothelial cell was studied in cholesterol-fed rabbits. Thirtyrabbits were randomly divided into five groups. The negative control group was fed with a standard diet; the positive control group was fed with the same diet with 2% cholesterol; the quercetin group was fed with the same diet with 2% cholesterol and quercetin 50, 100 or 150 mg/kg BW/day. The cholesterol-rich diet significantly increased Malondialdehyde (MDA) in the aortic blood vessels, as reflected by Thiobarbituric Acid-Reactive Substances (TBARS), inhibited endothelium-dependent vascular relaxations to acetylcholine, and decrease tissue content cyclic GMP with vessels from normal rabbits (negative control). In cholesterol-fed rabbits, quercetin treatment decreased MDA in plasma production, improved endothelium - dependent relaxations to acetylcholine, and increase cyclic GMP production. These results suggest that quercetin not only improves endothelium-dependent relaxations but also reduces lipid peroxidation (malondialdehyde) in the aorta and enhanced the tissue content cyclic GMP in hypercholesterolemic rabbits. These findings suggest that quercetin might play an important role in the protective effect on endothelial dysfunction in hypercholesterolemia.
Key words: Quercetin, malondialdehyde, endothelium-derived relaxing factor (EDRF), cyclic GMP.
Abbreviations: MDA, malondialdehyde; EDRF, endothelium-derived relaxing factor; NO, nitric oxide;TBARS, thiobarbituric acid reactive substances; and SOD, superoxide dismutase; TCA,trichloroacetic acid; BW, body weight.
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