EFFECT OF ESTROGEN ON CARDIOVASCULAR STRUCTURE IN UNINEPHRECTOMIZED ALBINO RATS: HISTOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY
Tarek A. El Ghamrawy
Department of Anatomy, Faculty of Medicine, Cairo University
Background: The risk of cardiovascular diseases increases greatly in postmenopausal female patients. The protective effects of female sex hormones, particularly estrogens were thought to be involved in protection against coronary heart diseases and hypertension. The aim of this work is to address the role of estrogen in protecting the cardiovascular system in hypertension and to find out its effects on myocardial blood vessels and aorta.
Material and methods: Fifty female albino rats were divided into four groups: (G1) control group, (G2) uninephrectomy sham ovariectomy given sesame oil as vector, (G3) uninephrectomy bilateral ovariectomy with sesame oil and (G4) uninephrectomy bilateral ovariectomy with estradiol (E2) replacement. Control group was fed on normal salt diet while the remaining groups had high salt diet. The left ventricle and aorta were excised for histological and immunohistochemical studies using vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (e.NOS) and morphometric analysis.
Results: The number of intramyocardial capillaries significantly decreased in G3 and increased in G4. In G2 and G3, the myocardium showed thickening of the tunica media of intramyocardial arterioles and increased fibrosis in between the myocardial cells. Also, the aorta had thickened tunica media and rupture of its smooth muscle fibers with roughening of its endothelial lining. In G4 the intramyocardial arteriolar wall thickness was significantly reduced. The fibrosis diminished markedly. The aorta showed uninterrupted and compact smooth muscle fibers and elastic fibers. Immunoexpression of VEGF and e.NOS in the myocardium dropped significantly in G2 and G3 while, in G4 the expression of VEGF had been restored to control values.
Conclusion: Estrogen ameliorated considerably the hypertensive structural changes in the myocardium and aorta. It exerted angiogenic and vasodilator effects, possibly through stimulating the production of VEGF and e.NOS.