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Biology of Reproduction, Vol 20, 253-260, Copyright © 1979 by Society for the Study of Reproduction
1 Department of Veterinary Physiology and Pharmacology,
The Ohio State University,
1900 Coffey Road,
Columbus, Ohio 43210 The biochemical and physiological characteristics of the uterine estrogen receptor (ER) were
compared between lean and infertile, fatty rats of the Zucker strain. After ovariectomy, the
amount of ER in the fatty rat uterus was less than half that found in the lean rat uterus. Also,
following 5 or 11 daily injections of 10 µg estradiol-17 ER levels were also measured in the hypothalamus and anterior pituitary. Hypothalamic levels
of the ER of fatty and lean rats were similar, but the fatty rat pituitaries had lower amounts of ER
as compared to pituitaries from lean rats. Also, the wet weights of fatty rat pituitaries were lower
than those from lean rats. Our data shows that the infertility in the Zucker obese rat is accompanied by physiological changes in the estradiol-receptor interaction in the uterus. Whether these
changes contribute to the observed infertility is unknown at this time.
(E2), the levels were significantly lower in
the fatty rats. The equilibrium dissociation constants of the cytosol and nuclear ER were similar in
both types of rats, as were the S values after sedimentation of the ER through 5-20% sucrose
gradients. When nuclear translocation and cytosol replenishment of the uterine ER were examined,
however, it was found that the peak of nuclear retention of the ER after an injection of E2 occurred
after 1 h in the lean rats and after 2 h in the fatty rats. Cytosol replenishment, moreover, was less
in the fatty compared to the lean rats. The peak of nuclear ER retention correlated with the peak
of in vivo uterine RNA synthesis as measured by a 1 h pulse of [3H] uridine incorporation in vivo.
The lean rats, however, also showed a second peak of incorporation occurring 8 h after E2 injection. This second peak was not observed with the fatty rat.
Note:
ACKNOWLEDGMENTS
Supported by research grants HD-08576 from the
National Institute of Child Health and Human Development and PCM 77-08533 from the National Science
Foundation. We thank Mrs. Arlene Myers for her
excellent help in the preparation of the manuscript.
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