effect of estrogen on endothelial permeability of aorta and the level of serum nitrite concentration in cholesterol-fed ovariectomized rabbit

Estrogen Replacement Therapy [ERT] in postmenopausal women may decrease the risk of Coronary Artery Diseases [CAD]. We hypothesized that Nitric Oxide [NO] releasing due to ERT may be the essential factor by which endothelial permeability decreases. Four groups of ovariectomized rabbits were under investigation for five weeks. Groups 1 and 4 received high cholesterol diet and other two groups [2 and 3] had normal diet. Estradiol valerate [5 mg] was injected weekly in groups 1 and 2. Blood samples were taken before and after the experiment. Finally, the animals were sacrificed for endothelial permeability determination and pathological investigation of aortae. After five weeks, the total cholesterol, triglycerides, HDL and LDL were significantly different between high cholesterol fed and normal diet groups [P<0.05]. In cholesterol-fed groups, triglycerides concentration was also different significantly [P<0.05]. Nitrite concentration was increased significantly in group 1, and it was different from other groups [P<0.05]. A considerable decrease of aorta permeability was obtained in group 1 but it was not significantly different from group 4 [P<0.1]. The considerable existence of fatty streaks was observed in the animals aortae of group 4, and it was significantly different from group 1 [P<0.05]. It suggests that prevention of intimal collection of foam cells and fatty streak in aorta by estrogen may be exerted by NO production