Effect of Pregnant Mare’s Serum Gonadotrophin, Estradiol and Progesterone on Superovulation in the Immature Rat

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Abstract
A dose-response relationship was observed between administered PMS and the number of ova shed in the HCG-ovulated immature 25-day-old rat with 30 IU PMS as the optimal dose. When a total dose of PMS of 30 IU was divided, administration of the second dose at 24 hr after the initial dose increased the number of ova shed, but no such increase was seen with the second injection either before or after this time. A marked increase in the number of ova shed also results from a single dose of 1 μg estradiol-17β given 24 hr after PMS stimulation. The estrogen also had no influence when given before 24 hr, but at this dose it reduced ovum numbers when given 42 hr or more after PMS. The number of eggs to be ovulated is therefore not fixed by 24 hr after initial stimulation and still may be influenced. Progesterone, in a 2 mg dose injected with or at various times after PMS, had no effect on the number of ova shed. (Endocrinology75: 586, 1964)