Delayed Implantation in Gonadotropin-Treated Immature Rats.

Abstract

Summary A single injection of 20 IU PMS on Day 30 and 1.2 IU HCG intravenously on Day 32 caused superovulation in the rats and, if mated on the evening of Day 32, an average of 22.8 implantation sites on Days 10 to 13 of pregnancy. Thirteen to 26 blastocysts were recovered from the uteri of the rats ovariectomized on Day 3 of pregnancy and given 2 mg of progesterone daily starting on Day 3. Implantation of these blastocysts was induced by a single injection of 1 μg estrone. An average of 17.3 sites was obtained when 20 IU PMS plus 1.2 IU HCG was used, and 7.7 sites when 10 IU PMS was given. The method for inducing superovulation provides the means for obtaining large numbers of blastocysts on Day 4 or 5 post-insemination, and large numbers of delayed blastocysts by a combination of treatments which cause superovulation and delayed implantation.