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Biology of Reproduction, Vol 22, 1029-1039, Copyright © 1980 by Society for the Study of Reproduction
1 Department of Zoology,
University of Maryland,
College Park, Maryland 20742 Experiments were conducted to investigate regulation by prolactin (PRL) of luteal, and possibly of adrenal, cholesterol ester hydrolase (CEH) in mature, pseudopregnant rats, and to correlate
changes in CEH activity and serum PRL, luteinizing hormone (LH) and progesterone (P) concentrations. 2-Br- Injection of 2 mg P with EC at either 1100 h and 2300 h PP5, or only at 2300 h PP5, had no
effect on luteal CEH activity at 1200 h PP6. None of the treatments had any effect on adrenal
CEH activity or on serum LH concentrations, except for one treatment (injection of EC plus oPRL
at 1100 and 2300 h PP5 followed by sacrifice at 0600 h) which significantly decreased serum LH. These data indicate that in mature pseudopregnant rats, PRL stimulates luteal CEH activity and
concomitantly increases serum P concentrations. A time interval of 6-9 h after exogenous or
endogenous PRL is both necessary and optimal for stimulation of luteal CEH. Both PRL surges are
necessary for complete luteal function, but the nocturnal surge appears to exert the greater influence on the parameters studied. The action of PRL on luteal CEH does not seem to be mediated by
P at concentrations of P injected, and under conditions of these experiments PRL had no effect on
adrenal CEH.
-ergocryptine (EC), EC plus ovine PRL (oPRL), or EC + P were administered to
mature rats on pseudopregnancy Day 5 (PP5) and/or PP6. Injection of EC at 1100 and 2300 h PP5
drastically reduced serum PRL concentrations at 1800 h PP5 and 0600 h PP6, indicating that both
the diurnal surge of PRL on PP5 and the nocturnal surge of PRL on PP6 had been successfully
blocked. Luteal CEH and serum P measured at these time periods were not affected. However, by
1200 h PP6, both were significantly decreased. Injection of oPRL with EC significantly increased
luteal CEH at 0600 h and 1200 h PP6, and significantly increased serum P by 1200 h PP6. However,
injection of oPRL at 1600 h PP5 and 0300 h PP6 after EC at 1100 and 2300 h PP5, had no effect
on luteal CEH at 0600 h, even though serum P at that time was significantly increased. Blocking
only the nocturnal PP6 PRL surge by injection of EC at 2300 h PP5 caused significant reductions
in both luteal CEH and serum P by 1200 h PP6, but these decreases were not as great as those
observed after elimination of both PRL surges. Injection of oPRL at 0300 h PP6, 4 h after EC
(2300 h PP5), significantly increased both luteal CEH and serum P by 1200 h PP6.
Note:
ACKNOWLEDGMENTS
The authors gratefully acknowledge NIAMDD for
the gift of materials used in the PRL and LH radioimmunoassays, as well as for the ovine PRL used for
injections. We also want to thank Sandoz, Inc. for
generously supplying the 2-Br--ergocryptine. Finally,
we wish to express our appreciation to Dr. Dennis
Hoover, University of Maryland School of Medicine,
and Dr. Susan Smith, University of Masaachusetts
Medical School, for helpful discussions during the
conduct of these experiments. We also wish to thank
Dr. Andrzej Bartke, University of Texas Health
Science Center at San Antonio, for assistance in the
preparation of this manuscript, and Ms. Gretta Small
for her excellent typing.
This article has been cited by other articles:
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  C. Stocco, C. Telleria, and G. Gibori The Molecular Control of Corpus Luteum Formation, Function, and Regression Endocr. Rev., February 1, 2007; 28(1): 117 - 149. [Abstract] [Full Text] [PDF]
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