Analysis of Superovulation in the Adult Hamster

Abstract

Hamsters injected with 30 IU of pregnant mares' serum (PMS)1 on Day 1 of the estrous cycle ovulated an average of 70 eggs, with the duration of ovulation and cycle length slightly prolonged. If one ovary was removed at the time of PMS treatment, the remaining ovary ovulated 34.8 eggs. The injection of 30 IU PMS at Day 2 or 3 lengthened the estrous cycle to 6 and 7 days, respectively, and resulted in the ovulation of approximately 45 ova. After similar treatment at Day 4, only 10 eggs were ovulated on the very next morning, but 56 eggs were released at the following cycle. These experiments, in conjunction with other observations, suggest that the hamster ovary develops approximately 10 large follicles on Day 1 but has an additional 25 follicles in reserve that can be stimulated if increased amounts of FSH are available. In the event that PMS is injected after Day 1, the normally developing follicles eventually become atretic, thus limiting final maturation to the reserve follicles.