[Action of LH on the secretion of estradiol by the chick embryonic ovary in in vitro culture].

Gonads from 7-to 18-day-old female chick embryos were cultured in vitro in the presence or in the absence of bovine LH, and the amount of oestradiol released into the culture medium was determined by radioimmunoassay. Depending on the stage investigated, one ovary secreted 2.8-28 ng oestradiol during a 24-h culture. LH stimulated oestradiol secretion at all stages studied. The stimulation coefficient was highest for the younger stages. The lowest concentration which gave a positive result was 10 ng/ml. The discrepancy between the strong action of LH in vitro and its apparent absence of action in normal development is discussed.