THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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sheep ìiver as receptor and sheep hormone(opl) as standard.
In the present study we have identified and
quantitated factors w.ith placenta'l lactogen_like activity not only
in the placental extracts of prlmates (human and monkey) and
ruminantS (sheep, goat) but also in the mouse and guinea pig.
To our surprise, we could not detect pl-like activity in the
placenta'l extracts of cow, dog, rat, horse and rabbit. In contrast,
prolactÍn-like activity has rreen detected in the placenta'l extracts
of human, monkey, sheep, goat, mouse, guinea pÍg, cow, dog, rat, but
not in horse and rabbit by the RRA-PRL. By employlng RRA_GH, GH_like
activîty has been detected in the placental extracts of primates
and ruminants, At the present, we are puzzled at the discrepancy
among r the results obtained from RRA_pRL and RRA_PL. It is not
clear why lactogenic activity could be detectecl iri the,'úlacenial
extracts of cow,.dbg, and rat by RRA-pRL but not by RRA_pL. One
of the possible expìanations courd be that stnucturaily the molecu'res
of placental lactogen of cow, dog, and rat are more simllar to opRL
than to oPL. Clearly, more deflnitive conc.lusions will be obtained
only following the purifìcation of the respective lactogens.