Reactions of Immature Rabbit Ovary to Gonadotropic Extracts

Abstract

The reactions of the prepubertal rabbit to gonad-stimulating extracts of anterior pituitary and of pregnancy urine have been extensively studied^1-9 but apparently no ovarian responses have been observed in this species at periods prior to the appearance of antrabearing follicles. Since the rat^10-13 and guinea pig 14 , 15 show luteinization of the theca cells in response to injections of similar extracts at an age when the follicle granulosa is still non-reactive, it was of interest to reexamine the immature rabbit with particular reference to possible reactions of an analogous nature.

White rabbits from a single stock, and representing age groups of approximately 15, 30, 45, 60 and 90 days, were used. (Table I.) Each group comprised 2 litters totalling 10 to 14 females. At the beginning of the experiments, one ovary was removed from 5 or 6 of the animals of each group to provide control material. One-half of the animals received an extract of sheep anterior pituitary, and the remaining half an oestrin-free extract of pregnancy urine. One-quarter cc. of the pituitary extract was equivalent to one luteinizing rat unit; ascending doses from 0.5 to 1.5 cc. were injected subcutaneously twice daily for 14 days. Ten γ of the pregnancy urine extract (A.P.L.) represented one luteinizing rat unit; 100 such units were given intravenously once daily for 14 days.

A few animals were killed at intervals, during the injections, but the majority were killed on the 15th day. The ovaries were sectioned serially, except in a number of instances where they were stained for lipoids by frozen section technique. In addition to these, a large number of control ovaries from mature rabbits (normal, treated and hypophysectomized) was studied.