THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

RAT CHORIONIC GONADOTROPTN:
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Until now, there is no conpelling ev.idence for the
existence of rat chorionic aonadotropin(rCc). Although early studies
by Pencharz and Lyons(193 3), Se'lye et aì('1933) , Astwood and Greep
(ISSA¡, and Averjll et al(t950) demonstrated that rat placentas
possess luteotropic property with the highest actjvity in day l2
placentas, subsequent studies by Matthies (1965,1966,1967;.l97ì),
Cohen et al(i969) demonstrated that the mammotropic activity is also
present in the day 12 placental extracts and maternal sera Thus
these investtgators suggest that the luteotropic activity of the
piacentas detected by early studies may be due to rat chorionic
manmotropi n or rat placental lactogen, since p.ituitary pro.lactin is
also shown to be luteotropic. The most convincing piece of evidence
for the existence of rat chorionic gonadotropin is provided by
cheng(1975) and Haour et al(.1976). By emp'loying radioreceptor assay
for gonadotropi n ( RRA-LH ) , Cheng(.l975) identified rat chorionic
gonadotropin from day 12 placental extracts but not on other days
of pregnancy. The elution volume of rCG after gel fiìtration on
Sephadex G-100 was identical to the ìarger species of rat chorionic
marrnotropin and l25I-rat luteinizìng hormone (30,000 to 32,000 M.W.).
Innunologicaìly, rCG cross-reacted poorìy wÍth rabbit anti_rLH but
the s'lope of the dilution-curves of both rCG and rLH was the same.
However, rcG has not been purified and its, chemicar properties remain
uncl ear.