An increase incidence of cardiovascular disease after menopause has been generally observed but the causal mechanisms are not fully understood. Since the changes of lipid profiles account for less than 40% of this relationship, direct effect of
estrogen
on vessel has been suggested. In this study, the effects of bilateral oophorectomy (OHX) were evaluated in 10 week old female Sprague-Dawley rats. Two months after sham(n=7)and OHX (n=10), the thoracic aorta was removed and placed in cold Krebs
solution. The thoracic ring, 3~4 mm in axial length, was suspended to force-displacement transducers connected to a polygraph and stretched to a resting tension of 2.0 gm. After 1 hour equilibration. Aortic ring was precontracted by
norepinephrine
10-7M. At plateau response of norepinephrine, acetylcholine (endothelium-dependent vasodilator) and sodium nitroprusside (endothelium-independent vasodilator) were applied and percent relaxation from precontracted level was assessed. In the
presence of
acetylcholine 10E-7M, and Sodium nitroprusside 10E-9M, 10E-8M, the percent relaxation of OHX rats were significantly decreased than those with sham operated rats. Usually 2~3 ring were obtained from one rat. Another aortic rings were fixed in 10%
formalin for 24 hours. Hematoxylin and eosin and Verhoeff-van Gieson stains were done for observe morphologic changes. Compare to sham operated rat aorta, subendothelial layer was thickened, elastic lamellae of tunica media were stretched and
disconnected, interlamellar space was widened and smoth muscle cells were proliferated in OHX rats.
From the above findings. It might be suggested that opphorectomy induce typical atherosclerotic morphological changes and decreased not only endothelium dependent vasodilatation but also endothelium independent vasodilatation.
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