Abstract:
Corticotropin-releasing hormone (CRH), a potent neuropeptide, is
produced by the placenta of anthropoid primates. No other mammals,
including prosimian primates, are known to produce placental CRH. In
humans, placental CRH appears to play an important role in the
progression of pregnancy to parturition. Maternal circulating CRH
begins to rise early in pregnancy and increases until parturition. Gorillas
and chimpanzees share this pattern of increasing maternal CRH during
pregnancy with humans. In humans, chimpanzees, and gorillas, maternal
CRH and estradiol concentrations are correlated, consistent with the
hypothesis that CRH is involved in the biosynthetic pathway for placental
estrogen production. In contrast, in baboons, maternal circulating CRH
rises precipitously early in pregnancy and then declines, though CRH is
detectable until birth. This research was designed to investigate the
pattern of maternal circulating CRH in the common marmoset during
pregnancy. Blood samples were taken across gestation from nine subjects
over 11 pregnancies, and the plasma was assayed for CRH. The pattern of
maternal circulating CRH in the common marmoset was similar to that
of the baboon, with a rapid rise starting at about 50 days postconception
and a peak at approximately 70 days postconception. By 110 days
postconception, CRH concentration had plateaued at a significantly lower
value. The peak and mean values for CRH were associated with fetal
number (e.g., females gestating triplets had higher values than females
gestating twins). Urinary estradiol showed no association with plasma CRH concentration. Marmosets appear to differ from the great apes in
this regard, and to share a pattern of maternal CRH during pregnancy
with the baboon, indicating that the baboon and marmoset pattern may
be ancestral. The function of the early rapid rise of CRH in baboons and
marmosets, and the significance of this difference between monkeys and
apes, are not known.
