THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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(iii) Human Chorionic CortlcotTôpin (hCC):
. EvÍdence regarding adrenocort ica I -s t,imulatíng
act,ivity from placental sources have been published
over t,he past 24 years. As sunrnarized by Genazzani et al
(1975), several authors have observed increased levels of
free cortisoL and ACTH in the plasma of pregnant women,
but others failed to confirm this. The occurrence of
adrenocorticotropic act.ivity in placental extracts has
also been reported by a number of authors, but in reviewing
these, Saxena (1971) could not, exclude ACTH present in maternal
blood contaminating the placental extract.s. However,
recently Genazzani et al (I974, 1975) have demonstrated
accumul-ation of ACTH irnmuno-reactive components in slices
of placental , and Rees et aI (1975) observed an increase
in plasma levels of ACTH during pregnancy that could not
be suppressed by admínistration of dexamethasone, which is
well known to inhibit ACTH release from the pituitary gtand.
According to Genzazzani et aI (L975) and Rees et al (1975),
use of optimal new techniques for measuring plasma ACTH sholrs
progressive increases in ACTH throughout pregnancy to near
term vrith maximal level_s three to four times above normal
(60 pg,/m1) compared to 16-20 pg/ml in nonpregnant women).
The ACTH content of placental extracts reported by Genazzani
et a] (1975) corresponds to about 7 pg per placenta, which
Ìs much lower than the amounts of hCG and hpL recovered,
from placentas "