Estrone and estradiol concentrations in peripheral plasma of laying hens as determined by radioimmunoassay

Abstract

An application of radioimmunoassay to measurement of concentrations of estradiol and estrone in peripheral plasma of hens is described. Evidence is presented that the estradiol measured by the procedure was essentially estradiol-17β.For 13 ovulatory cycles the average concentration of estradiol was 123 pg/ml with a range from 36 pg/ml to 284 pg/ml. The corresponding average concentration for estrone was 64 pg/ml with a range from 14 pg/ml to 138 pg/ml. For 12 days of no ovulation the average concentration of estradiol was 142 pg/ml with a range from 42 pg/ml to 364 pg/ml. The corresponding average value for estrone was 91 pg/ml with a range from 18 pg/ml to 242 pg/ml.The results are interpreted as demonstrating the existence of peak levels of plasma estradiol at 22–18 h and again at 6–2 h before ovulation, and a minimal level at 14–10 h before ovulation. The corresponding plasma estrone concentrations displayed a similar cycle but the earlier peak and the minimum occurred 2–4 h later than the corresponding values for estradiol. Such peak values were not demonstrable on days when ovulation did not occur.The results are discussed briefly in relation to variation in the levels of blood progesterone during the ovulatory cycle.