THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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that of hPL and hGH (Shome and Friesen, I9ZI) " The
primary Structure of mPL has not yet been determined.
Inununochemical studíes of mpI,, hpl,, hGH, reveAl
that mPt cross-react to a greater extent with antiserum
to hcH than does hpl, (Belanger et, al I I97J_; Vinik. et aL,
1973). In the radíoimmunoassay for mplf placental êxtract.s
from all monkey species cross-reacted equally weli, whereas
human and monkey growth hormone, and hpl, reacted poorly,
and pituitary prolactins do not cross-react at. alL in
the assay system (Friesen et aI , LgZI; Viník et al , l9?3).
(iii) Cell--origin and Pattern of Secr.etion of mpl,:
Friesen (1968) is the first one who studied
the biosynthesis of mpL from monkey placentas. Using
inmunofl u orescent staining technique (antibodies to hcH),
it, has been demonstrated that mpL is synthesízed in the cyto-
pLasm of the syncytÍotrophoblast (Currie eÈ aI, L966,
IkonÍcoff et, al , 1971).
Using radioimmunoassays for mpl,, it was found that
the secretion of mpI, ând hpl, are very simil-ar. mpl, was
detectable at 22 days of gestation, ho$rever, at day 42 the
mPL titers averaged 1.5 US/ml and increased throughout
pregnancy to reach a mean concentration of lI p grlml at
t,errn, whereas mPL jn umbilical_ vein blood was Less than 100
ng,/ml (Belanger et al, I97l; walsh et aI n L9771. After
delivery. maternal mPL concentrations decreased rapidly
with a half-time disappearance rate of 20 minutes as compared