Ki-67 antigen expression in the mammary epithelium of female rats in persistent estrus treated with raloxifene.

To evaluate Ki-67 antigen expression in the mammary epithelium of female rats in persistent estrus treated with raloxifene.Forty-one Wistar-Hannover rats in persistent estrus induced by 1.25 mg of testosterone propionate were randomly divided into two groups: Group A (control, n = 21) in which the animals received only the vehicle (propylene glycol) and Group B (experimental, n = 20) in which the rats received 750 µg/day of raloxifene by gavage. After 21 days of treatment, all the animals were sacrificed and the first pair of abdominal-inguinal mammary glands was extirpated and fixed in 10% buffered formalin to investigate Ki-67 expression by immunohistochemistry. The data were analysed using Student's t-test (p < 0.05).The percentage of Ki-67-stained nuclei per 500 cells in the mammary epithelium was 42.33 ± 6.18 and 15.51 ± 3.71 [mean ± standard error of the mean (SEM)] in the control and experimental groups, respectively (p < 0.001).Raloxifene treatment significantly reduced Ki-67 expression in the mammary epithelium of rats in persistent estrus.