Radioimmunoassay of oxytocin.
The evaluation of a radioimmunoassay of oxytocin is described. The method involved careful collection and transportation of blood at 4 degrees C, acidification of the plasma, extraction with Fuller's earth and radioimmunoassay using antisera raised in rabbits immunized against oxytocin conjugated to bovine serum albumin and 125I-labelled oxytocin. The antisera showed insignificant cross-reaction with a variety of small peptides including vasopressin and vasotocin. The limit of detection of the assay was 2.5 pg with intra-assay and interassay coefficients of variation of 7-15% and 12-18% respectively. Seventy-seven per cent (88 out of 116) of the pregnant women tested had detectable maternal plasma oxytocin. Serial samples of maternal plasma showed a significant increase in oxytocin from the first to the second stage of labour and a significant decrease in the third stage. Oxytocin concentrations in the umbilical arterial plasma were significantly higher in patients in labour. The significance of these findings is discussed.
D000918:Antibody Specificity; D005260:Female; D005312:Fetal Blood / Q000032:analysis; D006801:Humans; D007743:Labor, Obstetric; D010121:Oxytocin / Q000097:blood*; D011247:Pregnancy; D011863:Radioimmunoassay / Q000379:methods
D010121:Oxytocin