J. Anim Sci.
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J. Anim Sci. 1983. 56:1190-1197.
© 1983 American Society of Animal Science
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A Luteolytic Interaction between Estradiol Benzoate and Prostaglandin F2{alpha} in Cattle1,2,

J. E. Hixon, C. A. Pimentel, P. G. Weston, E. P. Chafetz, R. D. Shanks and W. Hansel

University of Illinois3, Urbana 61801 and and Cornell University,4, Ithaca, NY 14853

Abstract

A possible luteolytic interaction between prostaglandin F2{alpha} (PGF2{alpha}) and estradiol benzoate (E2 B) in cattle was investigated by randomly assigning 20 heifers to one of four groups of a 2 X 2 factorially designed experiment. The treatments for the groups consisted of im administration of: 1) 200 jug of E2 B, given twice daily on d 10, 11 and 12 of the estrous cycle plus 7 mg PGF2a, given at a separate site, but concurrently with the last injection of E2B; 2) the vehicles for E2 B (sesame oil) and PGF2{alpha} (saline); 3) E2 B and saline and 4) sesame oil and PGF2{alpha}. Administration of both E2 B and 7 mg PGF2{alpha} resulted in luteolysis as evidenced by a shorter mean length of die estrous cycle (P<.05) when compared with the vehicle-treated control group, and a decline in systemic concentrations of progesterone to less than 1 ng/ml in four of five animals. Administration of PGF2{alpha} with sesame oil was luteolytic in only one of five animals and E2 B plus saline had no effect on the mean length of the estrous cycle or systemic concentrations of plasma progesterone. These observations suggested a luteolytic interaction between E2 B and PGF2{alpha}. This luteolytic interaction was examined further in a second experiment. Corpora lutea were removed 12 h after treatment with 200 µ E2B or .5 ml sesame oil, administered twice on d 10, 11 and 12 of the cycle, and incubated with luteinizing hormone (LH) and PGF2{alpha} in vitro. The effect of both LH and PGF2{alpha} was to increase progesterone synthesis (P<.01), and this effect was observed irrespective of E2B pretreatment. These findings were not consistent with the hypothesis that the luteolytic site of action for either E2B or PGF2{alpha} was inhibition of the steroidogenic effects of LH as assessed under in vitro conditions.

Footnotes

1 Supported by NIH Grants HD-06718 and HD-11759

2 We are grateful to Carol Rickard, Raymond Saatman, Stella Vincent and Walter Crackel for their excellent assistance. We wish to thank the Upjohn Co. and Dr. James Lauderdale for providing the PGF2{alpha} used in this study. We are indebted to Dr. Gordon Niswender for the LH antiserum. We also thank the National Pituitary Agency, NIHMDD, for providing the bovine LH used in incubations and standards in the LH radioimmunoassay.

3 Depts. of Vet. Biosci. and Dairy Sci.

4 Section of Physiol., Division of Biological Sci.






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Copyright © 1983 by the American Society of Animal Science.