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Summary. Effect of LH on oestradiol secretion by the chick embryo ovary in organ 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.Introduction.

Summary ― Ovaries from decapitated, sham-operated and intact 18-day-old chick embryos were cultured in Medium 199 for 6 h, and the amount of 17f3-estradiol released into the culture media was determined by radioimmunoassay. Ovaries from decapitated embryos secreted significantly lower amounts of 17f3-estradiol than those from intact embryos, but there was no difference when they were compared to ovaries from sham-operated embryos in this respect. On an ovarian weight basis, 176-cestradio! production was significantly different between the 3 groups of embryos, the ratio being highest in the decapitates. 178