THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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syncytiotrophoblast (Tatarinov et al. 1976; Kin and HaLbert,
1976). In contrast, a nunber of other plasma proteins
increase during pregnancy, but are not absent from. plasma
of non-pregnant. subjects. One such is the rrpregnancy_
zone protein'r (FZP' similar to sp3 0f Bohn). vrhich is found
in placenta in proportion to the amount of retained maternar
blood; furthermore, immunof luorescent sÈaining for this
protein has localized it to the blood vessel walLs in the
placenta (Lin and Halbert, 1976).
Finally, the placenta is the site of formation of
the heat stable alkaline phosphatase found in the blood of
pregnant women in the latter part of pregnancy (Fishman
and chosh, L967). It has a moLecular weight, of 5g,000
including 3OE sugar residues (Sussman and GotÈlieb, 1969)
and appears on the plasma membrane covering the microvilli
of the placental surface, from which it is continuously
released into the maternal circulation as the membrane
undergoes renewal- (Hubstaert. et al, 1923). In the plasma,
the enzyme has a slow turnover rate (C1ubb et aL, 19?5),
so that the pLasma l-evel is maintained aLthough t,he placenta
contains relatively small amounts of the enzyme (Harkness,
1968). Wíth regard to the significanceof the changes in
plasma levels of this enzyne, Oesterling et al (I9ZZ) found
that the level was elevated in rnothers receiving insufficient,
dietary energy and that this elevatíon was moderately correlated
$rith a reduction Ín birth weight of the infant. They therefore
postulate that an eLevation in maternal cortisol levels due