THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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by B5%. In thls experiment, opl, opRL, and hpl did not lncrease the
specific bindjng activÌty of hCG to pseudopregnant corpora lutea.
Hówever, pre-treatment of the animals wtth either opRL, opl, or
hPL before PgFru adminlstration prevented the drastlc decrease of
gonadotropln blndlng acfivlty and the drop ln serum progesterone
produced by PgFru alone. Th.ls study suggests that lactogenic
hormones, particular'ly pìacenta'l Iactogens, can act like pRL in
maJntaining the LH-receptors in the corpus luteum.
In order to provlde evidence,¡¡ a possible Ínteraction
of exogeneous ìactogens on the. LH-receptors in the rat corpora
ìutea, animals were administered with ergocryptine (CBì54), a drug
known to depress protactin secretion in the rat (Shau and Clemens,
.1972). Figure 42 demonstrated that ìactogens were compìetely
effective in blocking the loss of LH-receptors and 1¡g decrease of
serum progesterone càLsed by cB-ì54, Thus, this Study demonstrated that
pìacentaì'lactogen cdn mafntain the corpus ruteum enhancJng its response
to LH and may indicate the mechahlsm oi lnterattìon of .thesè, hormones
in. the controì of corpus luteum function durínq pregnancy. . . :