THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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data argue for a close interaction between loss of corpus luteum
LH-receptor and progesterone, and that the effect of lactogenjc
hormone ls to prevent the loss of LH-receptor in the corpus
I uteum.
Treatment of rats with BromoergocryptÍ ne produced
a marked decreasê in progesterone production and the LH-receptor.
Bromoergocryptine suporesses. piolactin secretion
and simultaneous lactogenic treatment ( oPRL, or oPL, or hPL)
reversed the effect of ergocryptlne on both the LH receptor and
serum progesterone. It was of interest to observe that lactogenic
hormone treatment elevated the number of LH-receptors by ì.5 fold.
A previous report of Lee and Ryan (1975) showed that chronic
treatment ofsuperovulated rats for '10 days with estrogen increased
the capacity of ovarian tissue to bind gonadotropin. In the
above report it was suggested that the effect may have been due
to elevated prolactin. Certainìy, the effect of estrogen on elevat-
.ing circulating levels of prolactin Ìn rats is we'll
documented (Neì'l'l ,'1974). These reports in conjuction with the data
in the present experiment, support the hypothesis that prolactin
and placental 'lactogen may increase the number of LH receptors in
the rat corpus luteum and
prevent the decìine in the
number of LH receptors folìowìng treatment with PGF2ô or ergocryptine,
It is possible that the mechanism of lactogen-LH interaction
resides in the ability of lactogens to maintain the function of
iuteal cell LH-receptors.