Is the antiprogestin RU486 luteolytic in rats?

Abstract

Subcutaneous injections of RU486 on Day 1, Day 4 or Days 3 and 4 of pregnancy in rats induced abortion of the embryo and transient vaginal cornification. Nevertheless, most corpora lutea appeared to be functional at autopsy on Day 12. The same treatments in pseudopregnant rats also produced transient vaginal cornification, but did not terminate pseudopregnancy. This suggests that transient antagonism of progesterone by RU486 does not terminate function of the corpus luteum in rats and that positive feedback by progesterone is not essential for continuing luteal function in rats.