Hormonal Requirements for Implantation and Pregnancy in the Ovariectomized Rabbit

Abstract

After induced ovulation and insemination on day 1, followed by ovariectomy on day 2, a schedule of 1 mg of progesterone in two injections in oil per day on days 2-4 inclusive followed by 2 or 3 mg per day on days 5-9 inclusive was found to induce implantation in the majority of ovariectomized rabbits. Implantation percentages (102 x total no. of implants on day 10 -;- no. of corpora lutea) in different groups of 8-11 rabbits varied between 24 and 61 %; sham-operated and vehicle-injected controls gave overall significantly higher percentages of 57-79%. The addition of 0·1--0·5 p-g of 3,17f3- oestradiol to experimental groups at various times during these procedures resulted in implantation percentages of 49-63 %, but did not consistently improve them.