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Biology of Reproduction, Vol 17, 16-22, Copyright © 1977 by Society for the Study of Reproduction
-Estradiol.
I. Paradoxical Increase in RNA Synthesis
1 Reproductive Endocrinology Program,
Departments of Pathology and Anatomy, and Division of Biological Sciences,
The University of Michigan, Ann Arbor, Michigan 48109 In the pseudopregnant rabbit maintenance of the corpus luteum and progesterone secretion are
dependent upon the presence of 17
-estradiol. Withdrawal of estradiol causes a rapid decline in
progesterone synthesis, followed by a decline in weight of corpora lutea. In order to determine
some of the molecular events associated with this phenomenon, RNA and protein synthesis was
analyzed in corpora lutea at different periods after estradiol withdrawal. Within 48 to 72 h luteal
RNA and protein contents per unit DNA both declined, but no change occurred in luteal DNA
content. However RNA synthesis, measured by incorporation of [3H] uridine into RNA, increased
during the same period by as much as 100 percent. This increased rate of [3H] uridine incorporation could not be attributed to increased uptake of the radioactive precursor or to the rate of RNA
turnover. Cytological observations showed marked regressive changes in luteal cell structure. The
compelling evidence for regression of luteal cells after estrogen withdrawal suggests that the paradoxical increase in RNA synthesis might be attributed to activation of stromal cells in the regressing corpus luteum.
Note:
ACKNOWLEDGMENT
We acknowledge the skillful assistance provided by
Jack Spivak.
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