Effects of the antiestrogen anordiol on ovulation and endometrial histology in the rat.

The rat was evaluated as a model for the study of the folliculostatic properties of anordiol (2 alpha,17 alpha-diethynyl-A-nor-5 alpha-androstane-2 beta,17 beta-diol) which have been previously demonstrated in the primate. The effects in the rat were similar to those in the monkey in that anordiol: 1) extended the period of time for ovulation to occur, and 2) was effective only when administered during the early preantral stage of follicular development. The effect was different in that anordiol resulted in more complete luteolysis of newly formed corpora lutea. The presence of cornified cells in the vaginal smears 2 days after treatment with anordiol was a result of luteolysis and an intrinsic estrogenic activity of anordiol. Ovulation occurred on the first estrus after treatment whether the animals received 13 treatments every 5 days or only a single dose of anordiol. The uterine responses were characteristic of an antiestrogenic action of anordiol. It is concluded that the rat is a reasonable model for studies of the mechanism(s) of action of anordiol.