THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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than with prolactin-like effects. The growth_promotÍng actjvity
of oPL has been demonstrated convincing.ly in hypophysectomi zed
rats( Chan et a1 ,ì976), in which it not on.ly promotes body
weight but aìso st.imulates growth of the tibia.l cartilage as
shown in Table IX. But what GH-like effects of opl might be
observed during pregnancy m.ight be ascrjbed to opl ? By anaìogy to
hPL, one might expect opl to promote release from adipose t.issues
of free fatty acids to be used by the maternal tissues ( a glucose_
sparing effect) to ensure a steady source of avaltab.le energy for
the fetus, since glucose ìs the nain substrate for the fetus in the
ewe(Leat,lgTl). Thus, the bìnding of opl to adipose tissues is of
interest. However, recent reports from Handwerger et a.l (.l975:1976)
indicate that ìnjection of opL into ewes (both pregnant and non-pregnant)
caused a slgnificant decrease in piasma concentrations of free fatty
acid, suggesting that opL may be anti-lipolytic in vivo. Direct
confirmation of this anti-lipolytic effect of opl on sheep adipose
tissue in vitro would be welcome. In the rhesus monkey, opL aìso
seemed not to be lipoìytic ( prlvate comrunications with Dr. Ju.lane
Hotchkiss, Universì ty of pittsburg).
The fact that opL binds to lOO,O00 x g pel.lets obtained
from sheep ovaries and corpus luteun is of considerable interest. This
ìs especially true because in the case of the ovary, both oLH and
oPRL slfghtiy inhibited the binding of opl in a non-paraÏrel manner
whereas in other tissues they do not. The non-paraile'r lnhrbition
exhibited by oPRL and oLH are difficurt to lnterpret.One possibìe