PLASMA MEASUREMENTS OF CORTICOTROPIN-RELEASING HORMONE-BINDING PROTEIN IN NORMAL AND ABNORMAL HUMAN-PREGNANCY

Using corticotrophin-releasing hormone-binding protein (CRHBP) purified from human plasma and a 25 amino acid peptide corresponding to the C-terminus of CRHBP we have been able to produce rabbit polyclonal antisera specific for CRHBP. This has allowed the development of a radioimmunoassay which is able to detect CRHBP specifically in human plasma regardless of the presence of endogenous CRH. We have used this assay to estimate the level of CRHBP in non-pregnant human plasma to be approximately 20 nmol/l with a range of 9.1-40.6 nmol/l. We have also examined sequential plasma samples taken from 84 normal pregnant women at fortnightly intervals from 16 weeks gestation through to term. Four women were also sampled during labour and the first week postpartum. The median plasma level of CRHBP at week 16 of normal pregnancy was 21.59 nmol/l, levels rose slightly during the early part of the third trimester (26.76 nmol/l at week 30, (P < 0.01) and fell markedly towards term (19.72 nmol/l, P < 0.01) with only 8.70 nmol/l at labour. CRHBP levels returned to normal non-pregnant levels within 48 h of parturition suggesting a role for the fetoplacental unit in CRHBP production. In eight pregnancies complicated by diabetes, CRHBP levels at each gestational age were similar to those recorded for normal pregnancy. However, in pregnancies complicated by pre-term labour (n = 9) and pre-eclampsia (n = 7), plasma CRHBP levels were significantly reduced (P < 0.01).