Expression of the Ki-67 antigen in the endometrial epithelium of rats in persistent estrus treated with Exemestane

The present study aimed to evaluate the expression of the Ki-67 antigen in the endometrial epithelium of rats in persistent estrus treated with Exemestane. This is an experimental, randomized, and controlled study. Twenty-four adult Wistar female rats, virgin and in permanent estrus, were randomly distributed into 2 groups: group I - control (n=12) which received propylene glycol and group II - experimental (n=12) which received 10mg/kg/day of Exemestane (Aromasin®) diluted in 0.5mL of propylene glycol for 28 consecutive days. On the 29th day, the female rats were euthanized and the proximal third of the uterus was removed, placing them in 10% buffered formalin. Tissues were fixed in paraffin blocks, for later preparation of slides with standardized immunohistochemical study. Cells with brown colored cores were considered positive for Ki-67 expression. Comparative data between groups were analyzed using the Student's t test (p<0.05). The average percentages of stained cores with Ki-67 per 500 cells in the endometrial epithelium of female rats in permanent estrus was 169.8±6.8 and 87.3±9.4 in groups I (control) and II (Exemestane), respectively (p<0.0001). Exemestane administered at a dose of 10mg/kg/day, for 28 consecutive days, statistically significantly reduced the expression of Ki-67 antigen in the endometrial epithelium of female rats in permanent estrus.