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Biology of Reproduction, Vol 22, 837-845, Copyright © 1980 by Society for the Study of Reproduction
1 Institut D’Histologie, Faculté de Médecine,
Université Louis Pasteur,
67085 Strasbourg Cedex, France This study investigated the mechanisms of superovulation in 4-day cyclic female rats treated
with two successive doses of 150 µg/100 g BW FSH in the afternoon of diestrus 1 and in the
morning of diestrus 2. Following FSH treatment, a significant decline in LH release was observed
during the critical period of the cycle on proestrus at 1700 h. FSH release appeared to be completely prevented at this moment of the cycle. After pentobarbital (PB) administration on proestrus at 1330 h, ovulation failed to occur in FSH-treated females injected with a dose of 200 ng
LHRH i.v. This dose resulted in full ovulatory effects in control rats not treated with FSH. Infusion of 50 ng LHRH/h under PB blockade on proestrus, which caused a rise in blood LH within
30 min and resulted in full ovulation on the next morning in the controls, remained without effect
in FSH-treated rats. LHRH infusion of 1000 ng/h was necessary to induce superovulation and the
formation of an excessive number of corpora lutea with included oocyte in FSH-treated rats. A
decrease in plasma estradiol-17
concentration was observed at 2400 h during the night from
diestrus 2 to proestrus in FSH-treated rats. No changes in plasma progesterone concentration were
observed during the time period extending from the morning of diestrus 2 to the afternoon of
proestrus. Changes in the positive feedback action of estradiol on the hypothalamic pituitary
system were supposedly then involved in the decrease in pituitary responsiveness to LHRH in
FSH-treated rats.
Note:
ACKNOWLEDGMENTS
We wish to thank C. Lazarus and M. T. Kauffmann
for their excellent technical assistance and V. Tomasina for typing the manuscript. We would also like to
thank R. Dujol for preparation of the figures. We wish
to express our gratitude to Dr. A. F. Parlow for the
generous supply of NIAMDD reagents, and to Drs.
M. Jutisz and B. Kerdelhue for providing iodinated
hormones and reagents for determination of LH. We
are indebted to Dr. D. Beshara for his helpful linguistic assistance.
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