Corticotropin-releasing hormone in chimpanzee and gorilla pregnancies

In humans, the length of gestation and the onset of parturition have been l inked to the exponential production of placental CRH and a late gestational decline in maternal plasma CRH-binding protein (CRH-BP). CRH has been show n to have direct effects on the myometrium and on the fetal adrenal, where it stimulates production of the estrogen precursor dihydroepiandrosterone s ulfate. In vitro placental CRH production is stimulated by cortisol and inh ibited by progesterone. To determine whether this mechanism might operate i n other apes, we sampled eight chimpanzees and two gorillas through their p regnancies for CRH, CRH-BP, cortisol, estradiol, progesterone, and alpha-fe toprotein. We show that both chimpanzee and gorilla maternal plasma CRH con centrations rise exponentially as observed in the human. The gorillas exhib ited a human-like antepartum fall in CRH-BP, whereas CRH-BP in the chimpanz ee remained stable. Pregnancy-associated changes in cortisol, estradiol, pr ogesterone, and alpha-fetoprotein were qualitatively similar to those obser ved in humans. Maternal plasma cortisol correlated with plasma CRH in both gorillas (r = 0.60; P < 0.05) and chimpanzees (r = 0.36; P < 0.02). Further , there was a strong correlation between plasma estradiol and the log of pl asma CRH in the gorilla (r = 0.93; P < 0.0001) and in the chimpanzee (r = 0 .72; P < 0.001), which is consistent with the hypothesis that placental CRH determines the placental production of estradiol by stimulating the produc tion of fetal adrenal dehydroepiandrosterone sulfate. Plasma CRH and proges terone were positively correlated providing no in vivo support for progeste rone inhibition of CRH release.