The human placenta and fetal membranes express the corticotropin-releasing hormone receptor 1alpha (CRH-1alpha) and the CRH-C variant receptor.

Placentally derived CRH plays a major role in the mechanisms controlling human pregnancy and parturition. It has been suggested that there is a CRH placental clock that is active from the early stages of pregnancy and determines the length of gestation and the timing of parturition. CRH can influence human reproductive tissue function via specific CRH receptors. Two distinct CRH receptors have been cloned (R1 and R2) that share 70% homology at the amino acid level and exist as two alternatively spliced forms (alpha and beta). In this study we investigated the presence of CRH receptor subtypes in human fetal membranes derived from spontaneous rupture and placental biopsies at term. Using RT-PCR, we identified the full length of the CRH-R1alpha subtype in placental and fetal membranes. In both tissues we also identified a spliced variant of the CRH receptor (CRH-Rc). We were unable to detect any CRH-R2 messenger ribonucleic acid in any of the biopsies. Fluorescent in situ hybridization and immunofluorescence in both tissues demonstrated that syncytiotrophoblast cells and amniotic epithelium are the major cell types expressing CRH-1alpha and CRH-Rc receptor messenger ribonucleic acid. Further studies are necessary to give a better insight into the role of CRH and its receptors in these tissues.