The concentration of unconjugated oestrone, oestradiol-17 alpha and oestradiol-17 beta in the maternal plasma of the pregnant ewe in relation to the initiation of parturition and lactation.

Abstract

Summary. The concentration of unconjugated oestrone, oestradiol-17α and oestradiol-17β has been measured in the maternal jugular venous plasma of pregnant sheep every 6 hr over the period 108 hr before to 72 hr after parturition. Measurable levels of each oestrogen were present 108 hr before parturition and by about 40 hr, the concentration began to increase markedly. Levels of 200 to 350 pg/ml for oestrone and 100 to 150 pg/ml for oestradiol-17α and for oestradiol-17β were found just before parturition. At 12 hr after parturition, the concentration of oestrone and oestradiol-17β had fallen to < 15 pg/ml. Levels of oestradiol-17α remained elevated for a longer period after parturition and did not fall to <35 pg/ml until 48 to 60 hr after parturition.