Abstract
Background: Isoflavones are estrogenic compounds that exist in soy, clover, and peanuts. They are selective estrogen receptor modulators. Aim: The study was planned to explain the interactions of isoflavones with estrogen receptors alpha (ER alpha), beta (ER beta), and vascular endothelial growth factor (VEGF) expressions in ovarian and uterine tissues during different stages of the estrous cycle of regular cyclic female Wistar rats. Methods: Thirty-two regular cyclic females were divided equally into control group: fed casein-based diet and isoflavones group: fed casein-based diet and gavaged 50 mg/kg/day soy isoflavones extract 40%. The regularity of estrus cycles was monitored. Final body weight (FBW), weight gain (BWG), and ovarian and uterine weights were estimated. Histopathology and immunohistochemistry for ER alpha, Er beta, and VEGF in ovarian and uterine tissues were performed. Results: All females (100%, n = 16) in control group showed regularity in estrous cycle compared to 62.5% (n = 10) in isoflavones group. Estrus and diestrus phases revealed prolongation and shortening in isoflavones rats than control, respectively. Nonsignificant variation was noted in the duration of the whole cycle of both groups. FBW and BWG significantly decreased however, ovarian and uterine weights increased significantly in all estrous phases of isoflavones group than control. Histopathology demonstrated an increase in number of follicles/ovaries besides, hyperplasia and proliferation of luminal epithelium with hydropic degeneration in the isoflavones group. Also, uterine connective tissue stroma showed edema in the isoflavones group during all estrous phases. Immunostaining percentages of ER alpha, Er beta, and VEGF protein expression were significantly elevated in the isoflavones group during all estrous phases. Conclusion: Isoflavones induced irregularity of the estrous cycle that was encountered by increased and altered ER alpha, Er beta, and VEGF expressions in ovarian and uterine tissues.