Estrogenic uterovaginal effects of oral estetrol in the modified Allen–Doisy test

Abstract

Objective To evaluate the effect of estetrol (E₄) on vaginal cornification and uterine wet weight in the ovariectomized rat.

Methods Adult female rats served as experimental animals. Six groups of ovariectomized rats (eight per group) were treated orally once daily for 7 days as follows: vehicle (negative) control; E₄: 0.1, 0.3, 1.0 and 3.0 mg/kg/day, and ethinylestradiol 0.05 mg/kg/day as active (positive) control. Vaginal lavages were obtained daily and uterine wet weight was determined on day 7.

Results Vaginal cornification was observed by day 5 in all rats at all E₄ doses and in the animals receiving ethinylestradiol, but not in the control rats. The onset of cornification with E₄ was dose-dependent. After 7 days' treatment, the two highest E₄ doses (1.0 and 3.0 mg) induced statistically significant higher uterine wet weight compared to vehicle.

Conclusion Estetrol has estrogenic effects on the vagina and on the uterus of ovariectomized rats. The potency of E₄ is approximately 20-fold lower compared to ethinylestradiol.

Key words:

• ESTETROL
• E₄
• VAGINA
• UTERUS
• MYOMETRIUM
• ENDOMETRIUM