STIMULATION OF RABBIT OVARIES BY HUMAN CHORIONIC GONADOTROPHIN IN THE ABSENCE OF ENDOGENOUS GONADOTROPHINS

Abstract

SUMMARY The ovulatory response of hypophysectomized rabbits to 100 i.u. human chorionic gonadotrophin (HCG) i.v. declined progressively as the interval between pituitary removal and HCG injection was increased from 0 to 12 h. Hypophysectomized rabbits were also treated with HCG 2·5 h after receiving an ovary transplanted with vascular anastomoses from an oestrous donor. The proportion of grafts showing positive follicular responses to HCG in these recipients (2/4) was the same as in similarly treated intact recipients (1/2). It was concluded that endogenous gonadotrophins were not essential for HCG to stimulate follicular growth and ovulation. Therefore, the disappearance of gonadotrophins after hypophysectomy probably reduced the effect of HCG by inducing follicular regression and unresponsiveness rather than by removing synergistic hormones.