Maternal plasma corticotropin-releasing factor (CRF) and CRF-binding protein (CRF-BP) levels in post-term pregnancy: effect of prostaglandin administration

Objective: Placental corticotropin-releasing factor (CRF) affects myometrial contractility and the secretion of several uterotonins such as prostaglandins (PGs); however, the activity of CRF is counteracted by CRF-binding protein (CRF-BP). At term and pre-term labor, CRF levels in maternal plasma are highest whereas those of CRF-BP are falling, and the cause of this fall is unknown. Thus, in this study, we investigated the effect of PG administration for labor induction on maternal plasma CRF and CRF-BP concentrations. Design: Maternal plasma CRF and CRF-BP levels were assayed before and after (2 h later) induction of labor by intracervical administration of prostaglandin E2 (PGE2), and at delivery in a group of healthy post-term pregnancies (n=18). Controls were women at term out of labor (n=22), who subsequently progressed to deliver a healthy singleton baby. Methods: CRF was measured by two-site immunoradiometric assay, and CRF-BP was assayed by radioimmunoassay. Results: Maternal plasma CRF levels were significantly (PP2 were sufficient to increase maternal plasma CRF levels at delivery (P2 significantly decreased maternal plasma CRF-BP levels at delivery (P2 significantly reduced CRF-BP concentrations both after 2 h (PP Conclusions: In the light of the well-known stimulation of prostaglandin release by CRF, these data suggest a positive feedback effect of PGE2 on maternal CRF release during induced labor.