Influence of Age on the Response of the Immature Rabbit Ovary to Pregnant Mare’s Serum (PMS)

Abstract

Studies on the rat and the mouse have clearly demonstrated that ova production is dependent in part on the age of the animal. This study was made to determine the influence of age on the response of the immature rabbit ovary to 2 levels (50 and 200 IU) of PMS. One hundred nineteen strain III rabbits (New Zealand White origin), ranging in age from 41 to 155 days, were used in sibling groups of treatment and control. The immature rabbit ovary responds to PMS in a similar manner to that of the mouse and rat. The data obtained indicate an increased sensitivity to PMS with age to a peak, followed by a decreasing response. The response is portrayed macroscopically by ovarian and follicular size, accompanied by hemorrhaging. Microscopically, thecal disorganization, breakdown of basement membrane, and a change in granulosa cell size paralleled the relative ovarian weight change. The uterine response was also plotted as a function of age. This showed a similar but more varied response, indicating that PMS is involved, but that other factors are also involved in the regulation of uterine size and appearance. (Endocrinology75: 411, 1964)