THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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lowestlsys¡5 of ovine pituitary prolactin and peak ;levels of opl
are for¡nd in the circulation at about 95 days of pregnancy, the
time at which lactogenesis in the ovine maÍrrnary gland begins
(Denamur,l965). Thus, from these observations, it may be speculated
that marmogenesis and Jactogenesis ln the ewes are promoted
by oPL. However, binding studíes showed that less than 3% of specific
binding of oPL was found iri ovine marnmary glands. Thus , it is
possible that oPL may not have a direct effect orr ovine,
marmary gland but has an indirect effect through other endocrine
organs such as the ovary.
2. Metabolic Effect:
The only study to date which directly considers the
metabolic effects of opl in the sheep Ís that of Handwerger et al
(1976). In their studies, they fe¡¡¿ that opl admlnistration caused
an acute decrease in free fatty acid, glucose, and amino nltrogen
c.ncentrations. The effects observed were different from the effects
observed for hPL in human. In man, i ntramuscuì ar
administration of hPL caused an increase in fatty acid concentration
(Grumbach et al ,'1966). Thus, studies by Handwerger et al suggest
that oPL is impontant in the moduìation of intermediary metabolism
durÍng pregnancy but its effêct may be opposite to the effect of
ovine growth hormone in sheep.