Comparative Study of Tamoxifen and Raloxifene on Endometrial Cell Proliferation of Female Rats in Persistent Estrus

Abstract

ObjectiveThe objective of the study was to compare the effect of tamoxifen and raloxifene on the endometrium of female rats in persistent estrus, by Ki-67 protein expression.MethodsThe study comprised 60 Wistar-Hannover female rats in persistent estrus, induced by a single subcutaneous dose of 1.25 mg of testosterone propionate on the second day of age. At 90 days of life, the animals were randomly divided into 3 groups of 20 animals each. Group 1 (control), received only placebo; group 2, the animals were treated with tamoxifen, 250 μg/d; and group 3, the rats were treated with 750 μg/d of raloxifene by gavage during 30 days. Then, the animals were killed, and the endometrium was removed for immunohistochemical analysis of Ki-67 antigen expression. Statistical analysis was performed by β regression model (P < 0.05).ResultsMean percentages of Ki-67 protein expression in the endometrium of rats in persistent estrus were 43.21% ± 3.39%, 7.36% ± 0.95%, and 7.20% ± 0.76% in groups 1, 2 and 3, respectively (P < 0.001). There was no statistical difference between groups 2 and 3 (P = 0.7159).ConclusionsThe present results indicate that, at the doses and during the time of treatment used, both tamoxifen and raloxifene induce atrophy in a similar way of endometrial epithelium of rats in persistent estrus.