comparative histological and immunohistochemical study on the effect of dietary soya and estrogen therapy on the aorta of ovariectomized albino rats

ABSTRACT

Soya was proposed to improve endothelial dysfunction in ovariectomized rats, perhaps through a mechanism similar to estrogen. The present work aimed at studying the changes in the aorta of ovariectomized rats and demonstrating the comparable effects of soya bean to estrogen replacement therapy [ERT] on the aorta by histological and immunohistochemical methods. Thirty nine female albino rats were divided into four groups. Group I [control], included 9 rats. Group II included 10 ovariectomized rats. Rats of group III were left ovariectomized for six months and received estrogen replacement for two months later. Rats of group IV were left ovariectomized for six months and received dietary soya for two months later. Aortic sections were subjected to H and E, estrogen receptor [ER] and nitric oxide [NO] immunohistochemical staining. The media thickness and the optical density of NO immunoreactive cytoplasm of endothelial cells were assessed. In group II, strong esinophilic cytoplasm, dark nuclei, dislodged nuclei of endothelial cells besides focal denuded endothelial lining were noted. In addition, dark nuclei and perinuclear cytoplasmic vacuolation were seen in smooth muscle cells. Most of the elastic fibers were straight. ER immunoexpression was cytoplasmic in some fields, however, most fields exhibited-ve reaction. Faint cytoplasmic NO immunoreaction was recorded. Highly significant increase in media thickness and highly significant decrease in NO optical density were reported. In group III, most of the elastic fibers were straight, while other structural elements were comparable to the control. In group IV, few elastic fibers were straight and minimal increase in media thickness was observed. It could be concluded that dietary soya improved the changes recorded in the wall of the aorta of ovariectomized rats, which could suggest soya as a preferable therapeutic substitute to estrogen which was claimed to have side effects on the female genital tract. This suggestion was reinforced by less apoptotic endothelial cell nuclei and fewer straightened elastic fibers of the media