RADIOIMMUNOASSAY OF OESTRONE, OESTRADIOL-17α AND -17β IN BOVINE PLASMA DURING THE OESTROUS CYCLE AND LAST STAGES OF PREGNANCY

Abstract

SUMMARY Specific antibodies were raised against 6-(O-carboxymethyl)oxime—bovine serum albumin derivatives of oestrone, oestradiol-17α and -17β for use in radioimmunoassays to measure each unconjugated oestrogen in peripheral plasma during the bovine oestrous cycle and the last stages of pregnancy. In non-pregnant cows the concentration of oestradiol-17β increased from very low values of 5 pg/ml to 14 pg/ml at oestrus. Oestrone showed little cyclic variation with an average concentration of 4 pg/ml, whereas oestradiol-17α varied inconsistently at much higher levels between 20 and 30 pg/ml. An increase in the concentration of each oestrogen occurred in the last 14 days of pregnancy with a rapid decrease around parturition. Oestradiol-17β increased from 400 pg/ml on Day — 14 to 1000 pg/ml on Day — 1 with values of 300 pg/ml at parturition. Similar values for oestradiol-17α were 400, 800 and 500 pg/ml with a further decrease to 300 pg/ml, 1 day post partum. Higher concentrations for oestrone were observed: 900 pg/ml on Day — 14, 2800 pg/ml Day — 1, decreasing rapidly to 500 pg/ml on the day of parturition.