J. Anim Sci.
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J. Anim Sci. 1986. 62:422-427.
© 1986 American Society of Animal Science
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Concentrations of Ovarian and Pituitary Hormones Following Prostaglandin F2{alpha}-Induced Luteal Regression in Ewes Varies with Day of the Estrous Cycle at Treatment1

D. R. Deaver2, N. J. Stilley, R. A. Dailey, E. K. Inskeep, and P. E. Lewis

West Virginia University, Morgantown 265063

Abstract

Prostaglandin F2{alpha} (PGF2{alpha}) was injected on d 5, 8 or 11 postestrus in ewes to determine how stage of the estrous cycle would affect PGF2{alpha}-induced changes in concentrations of ovarian and pituitary hormones and intervals to the onset of estrus and the preovulatory surge of luteinizing hormone (LH). Initial concentrations of progesterone and average values during the 12 h after PGF2{alpha} were related positively to the day of cycle on which PGF2{alpha} was administered. Patterns of decline in progesterone after injection of PGF2{alpha} were similar among the 3 d. Concentrations of LH in plasma increased in a similar manner from 0 to 12 h in all ewes. After 12 h LH continued to increase, plateaued or declined in ewes treated on d 5, 8 or 11, respectively. Initial concentrations of follicle stimulating hormone (FSH) in plasma were related positively to day of treatment. After treatment with PGF2{alpha}, FSH increased within 2 h on d 5 but declined by that time on d 8 or 11. Concentrations of estradiol following treatment did not vary with day. The onset of estrus and the preovulatory surge of LH occurred at 36 and 35, 40 and 45, and 48 and >48 h in ewes treated on d 5, 8 or 11, respectively. It is concluded that: 1) the initial increase in LH is dependent on a decrease in plasma progesterone and 2) differences in patterns of secretion of gonadotropins before the preovulatory surge of LH might be caused by differences in progesterone or progesterone: -estradiol ratio when luteal regression is induced on different days of the estrous cycle.

Footnotes

1 Published with the approval of the Director of the West Virginia Agr. and Forestry Exp. Sta. as Scientific Paper No. 1954. Supported by Hatch Project 224 (NE-72). The authors thank Dr. R. L. Butcher for the antisera for progesterone and estradiol-17ß, Dr. G. D. Niswender for the ovine LH antisera (GDN#15), Dr. L. E. Reichert, Jr. for the purified ovine LH (LER1374-A) used for iodinations, Dr. D. J. Bolt for the reagents used to assay ovine FSH and Dr. J. W. Lauderdale and The Upjohn Co., Kalamazoo, MI for the PGF2{alpha}.

2 Present address: Dairy Breeding Res. Center, Dept. of Dairy and Anim. Sci., Pennsylvania State Univ., University Park, PA 16802.

3 Division of Anim. and Vet. Sci.






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Copyright © 1986 by the American Society of Animal Science.