Effects of cholesterol diets on vascular function and atherogenesis in rabbits

Vascular endothelial dysfunction is an important early event in atherogenesis. To evaluate the effects of different levels of cholesterol-containing diets on vascular function and atherogenesis, 17 New Zealand White male rabbits were randomized into four groups: Control with noncholesterol, 10-week 0.5% (0.5C-10) or 1% cholesterol (1C-10), and 14-week 0.5% cholesterol (0.5C-14) feedings. After 10 or 14 weeks, the aortas were harvested for studies of vascular endothelial function and percentage surface lipid lesions. The 0.5% and 1% cholesterol feedings resulted in the same degree of hypercholesterolemia independent of the level and period of cholesterol feeding. There was a decreased trend in vascular endothelial-dependent relaxation to acetylcholine in cholesterol-fed rabbits. Fourteen-week cholesterol feeding induced the least vascular dilation at a concentration of 10-7 M acetylcholine (-38 +/- 3%, -23 +/- 4%, -23 +/- 2%, and -15 +/- 5% in control, 0.5C-10, 1C-10, and 0.5C-14 groups, respectively, P = 0.003). More cumulative exposure of arterial walls to cholesterol induced more surface lipid lesions in the aorta (r = 0.877, P < 0.001). There was a negative relationship between aortic lesions and vasodilation (r = -0.557, P = 0.020 for calcium ionophore; r = -0.463, P = 0.062 for acetylcholine). We conclude that the 0.5% and 1% cholesterol feedings induce similar degrees of hypercholesterolemia. However, aortic lipid lesions and vascular reactivity are dependent on cumulative exposure to cholesterol rather than serum cholesterol level only. Furthermore, decreased vascular endothelial relaxation in cholesterol-fed rabbits was related to lipid plaques in the aorta.