[Secretion of estradiol by the ovary of the hypophysectomized chick embryo]

Ovaries from control and hypophysectomized chick embryos were cultured in vitro, and oestradiol released into the culture medium was determined by radioimmunoassay. At all 4 stages investigated, i.e., 11, 13, 15 and 17 days, the ovary of hypophysectomized embryos secreted less oestradiol than the ovary of control embryos. However, per unit weight of ovary, oestradiol production was clearly less in hypophysectomized than in control embryos only at the stage of 11 days. It is concluded that the hypophysis plays a part in oestradiol secretion by the ovary in the 11-day-old chick embryo.