THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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In conclusion, it is c'lear from the above data thqt a
limited amount of infornation .is available on non_primate p.lacental
'lactogens for comparat.ive studies. uritil now, only hpl,mpL, opl,
bPL, cPL, and rPL have been purlfied or partial.ly purified. Non_
prlmate p'lacental 'lactogens are lnrnunologically different from
primate placental ractogens. They ail have a slmilar rnorecurar
weight of 20,000 to 22,000 w.ith the exception of guinea pig and
hamster and including of cow. Blologlcally, it appears that
primate placental lactogens are less potent than pur.lf.ied
oPL and bPL in both lactogenic and somatotrophic assays particularly
when these hormones were tested slmultaneously in the radloreceptor_
assays for proìactin and for growth hormone. Furthermore, it is
apparent that the secretion pattern of all placental ìactogens are
very similar in most spec{es with the except.ion of mouse and rat
and possibly the cow. In mouse and rat, two peaks of
lactogenic actlvìty were observed during pregnancy instead of one
peak as seen in other species. Until now, no information
is. available on the amino acld sequence of placentaì lactogens
with the exception of human placental lactogen which is g0%
homoiogous with human growth hormone.