Influence of One or Two Ovaries on Ovulation and Ovarian Weight in the Hypophysectomized Rat

The aim of these experiments was to determine whether the availability of a greater amount of gonadotropins to an animal with a single ovary accounts for compensatory ovulation and increase in ovarian weight. Hypophysectomized immature rats were used, eliminating the influence of endogenous gonadotropins. Following a single injection of PMS, the changes in ovulation and ovarian weight, in response to HCG, were compared in animals possessing 1 or 2 ovaries. Under these experimental conditions, the single ovary of semispayed rats invariably weighed half as much as the combined weight of both ovaries of 2-ovary rats. On the day of optimal response to HCG, the single ovary also ovulated half as many eggs as the 2-ovary group. It is therefore concluded that increased availability of gonadotropins to the single ovary is not responsible for the compensatory changes. Increasing doses of PMS are required to increase the ovulation rate and ovarian weight of the single-ovary animals to the same levels as the 2-ovary rats. (Endocrinology82: 591, 1968)