UROCORTIN IN PREGNANCY

OBJECTIVES: The aim of this study was to investigate the possibility t hat urocortin is the ligand that displaces corticotropin-releasing hor mone from its binding protein ir the maternal circulation during pregn ancy and, if so, to determine whether urocortin, like corticotropin-re leasing hormone, is synthesized in substantial quantities in the place nta. STUDY DESIGN: A radioimmunoassay specific for urocortin was devel oped and used for measurement of the peptide in chorionic villi and fe tal membranes (amnion and chorion) from normal and preeclamptic pregna ncies. These tissues were also assayed for corticotropin-releasing hor mone. Assays for urocortin were also carried out on normal term pregna nt and nonpregnant myometrium End on plasma from nonpregnant individua ls, and assays for both peptides were performed on sequential normal p regnancy plasma samples taken from mid gestation until term. RESULTS: Corticotropin-releasing hormone was present in normal term (1904 +/- 4 89 pg/g) and preeclamptic placentas (5897 +/- 1526 pg/g) and in normal term fetal membranes (645 +/- 155 pg/g, n = 6 in all cases). Urocorti n was not detected in any of the tissues studied: nor was it found in the normal human plasma samples. Unlike the situation for corticotropi n-releasing hormone, no pregnancy-related pattern was seen for urocort in in the plasma from pregnant women. CONCLUSIONS: Urocortin is not tr anslated to any great extent in the pregnancy tissues investigated, no r is it present in the circulation of pregnant women in detectable amo unts. Furthermore, it is unlikely that urocortin is responsible for th e high maternal plasma levels of free corticotropin-releasing hormone circulating in the latter stages of pregnancy but this does not preclu de the possibility that another, as yet uncharacterized, corticotropin -releasing hormone-like peptide may be.