THE DISTRIBUTION OF RADIOLABELED CORTICOTROPIN-RELEASING FACTOR IN PREGNANT RATS - AN INVESTIGATION OF PLACENTAL-TRANSFER TO THE FETUSES

Stress during gestation can have serious consequences on the developme nt of the fetus. Many of these effects appear to be mediated by hormon es of the hypothalamic-pituitary-adrenal (HPA) axis. Corticotropin-rel easing factor (CRF), released by the hypothalamus during times of stre ss serves to activate release of pituitary hormones and is also presen t in law levels in rat plasma. Moreover, the uterus contains significa nt quantities of CRF at implantation sites, probably from local source s. Therefore, the possibility exists that CRF may cross the placenta a nd activate the fetal HPA axis. However, the ability of CRF to cross t he placenta has not been demonstrated. In the present study, pregnant rats were administered radiolabeled CRF intraperitoneally, and the dis tribution of the labeled product was determined in the Fetuses and var ious maternal organs. High levels of activity were observed in the pre gnant female's uterus, adrenals, heart and the placentae, but only bac kground levels of activity were detected in the maternal brain. Very l ow levels of activity were observed in the fetuses, indicating that th e transfer of CRF across the placenta is greatly restricted. These fin dings suggest that maternal CRF has little or no direct effect on the developing fetus during gestational stress. (C) 1998 ISDN. Published b y Elsevier Science Ltd.