Corticotrophin-releasing factor in human placenta: localization, concentration and release in vitro.

Corticotrophin-releasing factor (CRF) immunoreactivity was demonstrated by immunohistochemical staining in the cytotrophoblast of the early pregnancy placenta, in the decidua and in the amnion. This localization is different from that of adrenocorticotrophic hormone (ACTH) and beta-endorphin, which are present in the syncytiotrophoblast. The release of immunoreactive CRF was demonstrated from both early and term placental tissues in vitro. The mean amounts of CRF in the early and term pregnancy placental/decidual extracts were 0.99 +/- 0.5 ng/g and 19.7 +/- 3.1 ng/g, respectively. A slightly greater amount of CRF was found in extracts from term placentae and in cord venous plasma collected after spontaneous vaginal delivery than in those collected at elective caesarean section performed before the beginning of labour.