OESTRADIOL CONTENT OF OVARIAN VENOUS BLOOD AND OVARIAN TISSUE IN HYPOPHYSECTOMIZED RATS DURING LATE PREGNANCY

Abstract

SUMMARY Oestradiol-17β in ovarian venous blood and ovarian tissue was assayed by a competitive protein-binding method. Oestradiol was found in similar amounts in the ovarian vein blood of pregnant rats hypophysectomized on Day 12 and killed on Days 16 and 21 and in pregnant rats sham-hypophysectomized on Day 12 and killed on Day 16. The pituitary therefore plays no part in oestrogen production after mid-pregnancy until some time between Day 16 and Day 21, when it gives rise to an increased ovarian venous blood oestradiol content just before parturition, in intact sham-hypophysectomized rats. It is suggested that this increase is associated with the advent of the post-partum ovulation. The corpus luteum and the extraluteal component of the ovary in hypophysectomized rats autopsied on Days 16 and 21 and in sham-hypophysectomized rats autopsied on Day 16, contain similar amounts of oestradiol within each group. The extraluteal component contains about five times more oestradiol than corpora lutea in sham-hypophysectomized intact rats autopsied on Day 21. The ovaries of these animals also show an increased amount of oestradiol over that of the ovaries in the other three groups. It is suggested that secretion of oestradiol after mid-pregnancy in rats involves concurrently both the corpus luteum and the extraluteal component of the ovary.