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Biology of Reproduction, Vol 17, 535-540, Copyright © 1977 by Society for the Study of Reproduction

Luteolysis Induced by Prostaglandin F2agr Before and After Hysterectomy in Heifers

J. N. STELLFLUG 1, T. M. LOUIS 1, R. C. GOREWIT 1, W. D. OXENDER 1, , and H. D. HAFS 1

1 Animal Reproduction Laboratory, Department of Dairy Science, Michigan State University, East Lansing 48824


In a Latin Square design, each of 6 heifers was given (im) 5, 10 and 15 mg PGF2agr during diestrus during three consecutive estrous cycles. Then the uterus and cervix were removed. Thirty to 45 days after surgery, each hysterectomized heifer was given 30 mg PGF2agr to induce estrus before the same experimental doses of PGF2agr were resumed at 15-day intervals beginning 10 to 12 days after this induced estrus. Ten and 15 mg PGF2agr were luteolytic in 10 of 12 heifers before and after hysterectomy. While 5 mg PGF2agr was not luteolytic in intact heifers, it caused luteolysis in three of four heifers after hysterectomy. Thus, the uterus is not required for luteolysis induced by exogenous PGF2agr in heifers. To the contrary, the uterus may interfere with luteolysis induced by PGF2agr.

Serum (jugular) progesterone changes were similar for the first 6 h after 5, 10 or 15 mg PGF2agr in heifers before and after hysterectomy, whether or not PGF2agr was luteolytic. After the first 6 h, progesterone remained elevated at about 60 percent of pretreatment values in heifers which did not exhibit estrous behavior, while progesterone declined to less than 1 ng/ml within 36 h in heifers which exhibited estrus. Following the initial rapid decline in progesterone, serum LH doubled within 3 h after administration of PGF2agr and LH remained elevated until 6 h in all heifers; it returned to pretreatment values within 12 to 24 h when heifers exhibited no estrus, but it remained elevated when PGF2agr was luteolytic. Serum estradiol increased within 18 h when PGF2agr was luteolytic, and estrus began at 78 ± 5 h in these heifers. There was no rise in serum estradiol when heifers failed to exhibit estrus after PGF2agr. Thus, beginning within 18 h, elevated estrogen secretion may participate in the luteolysis begun by exogenous PGF2agr. Serum testosterone was unaffected by PGF2agr injections before or after hysterectomy.

Note:
ACKNOWLEDGMENTS This research was supported by USPHS Research Grant No. HD 06948 and published with approval of the Director of the Michigan Agricultural Experiment Station as paper no. 7958. Dr. J. W. Lauderdale (The Upjohn Company) supplied the PGF20 Tham salt, Dr. G. D. Niswender (Colorado State University) supplied the anti-progesterone (#869), Dr. L. E. Reichert supplied the highly purified bovine LH (LER-1072-2) for iodination, and NIH Endocrinology Study Section supplied the NIH-LH-B8 used as a standard in our assay. Part of this research was presented previously (J. Animal Sci. 41: 380, 1975).

Submitted on February 7, 1977
Accepted on June 3, 1977






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Copyright © 1977 by the Society for the Study of Reproduction.