Corticotropin-releasing hormone-binding protein in primates

In humans, placental corticotropin-releasing hormone (CRH) production has b een linked to the determination of gestational length, and a late gestation al fall in CRH-binding protein (CRH-BP) has been linked to the onset of par turition. Expression of placental CRH mRNA is limited to primates, and only in man has a circulating CRH-BP been described. As the fall in CRH-BP in l ate gestation has been associated with parturition in humans, we sought to determine whether a CRH-BP circulated in the plasma of other primates. It i s unclear whether maternal plasma CRH concentrations are elevated in New Wo rld monkeys and prosimians, We have therefore performed CRH plasma measurem ents in the blood of pregnant marmosets, in several species of lemur, and i n pregnant and fetal rhesus monkeys as a positive control. Using gel chroma tography, CRH-BP was detected in the human, gorilla, chimpanzee, orangutan, gibbon, macaque, squirrel monkey, and marmoset, but was absent in the mand rill, spider monkey, and lemur. CRH was detected in the plasma of pregnant marmosets and rhesus monkeys. CRH was also detected in the fetal rhesus mon key, but at lower concentrations than in maternal plasma. CRH immunoreactiv ity was not detectable in the plasma of pregnant lemurs or in extracts of l emur placenta. In conclusion, a circulating binding protein for CRH exists in all species of apes but occurs variably among New World and Old World mo nkeys and is absent in lemurs. The variable occurrence of the CRH-BP does n ot support a role for this protein in the mechanism of parturition in prima tes. Maternal CRH is elevated in the pregnant marmoset and rhesus, and may play a role in the pregnancy of New and Old World monkeys. (C) 2001 Wiley L iss, Inc.