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Biology of Reproduction, Vol 18, 643-651, Copyright © 1978 by Society for the Study of Reproduction
1 Department of Gynecology and Obstetrics,
University of Wisconsin Center for Health Sciences
Madison, Wisconsin 53706 Placental cotyledons were removed from 23 ewes of 120-130 days of gestation immediately
before and at intervals up to 24 h after the initiation of cortisol administration. The fetuses received 0, 4.8 or 24.0 mg cortisol/24 h i.v. Samples of arterial and venous umbilical blood were
collected from each fetus at 12 h intervals for cortisol determination by competitive protein-binding radioassay. Placental microsomes prepared from the fetal cotyledons were incubated with
radioactive dehydroepiandrosterone, androstenedione and testosterone along with appropriate
cofactors to measure the aromatizing activity (estrone and estradiol synthesis). The infusion of cortisol into fetuses 2-3 weesks prior to parturition significantly increased
plasma cortisol levels to those normally found in fetuses at birth. The correlations between umbilical arterial cortisol levels and corresponding aromatizing rates were not significant. The data
suggest that although the increased cortisol levels may have an effect on aromatizing activity,
the effect is not consistently significant and probably does not account for the increase in maternal
and fetal plasma estrogen surges before ovine parturition.
Note:
ACKNOWLEDGMENTS
We are grateful to M. M. Fischer, W. Santoski and
R. Weymouth for their technical assistance and to
P. L. Miller for typing the manuscript.
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