Effects of estradiol-17 beta, naloxone and gonadotropin releasing hormone on postpartum secretion of luteinizing hormone in fall-lambing ewes.
The interaction among exogenous estradiol-17 beta, naloxone and gonadotropin releasing hormone (GnRH) in the control of luteinizing hormone (LH) secretion was studied in intact postpartum ewes nursing their offspring. One-half of 30 fall-lambing ewes were implanted subcutaneously with an estradiol-17 beta containing Silastic capsule between postpartum d 1 and 12 which doubled their serum concentrations of estradiol (16.0 +/- .1 vs 8.4 +/- .1 pg/ml). Blood samples were collected from implanted and non-implanted ewes at 15-min intervals for 5 h on d 3, 8, 13, 20 and 28 postpartum. Pre-injection samples were collected for 1 h, and ewes were injected with saline, naloxone (NAL;1 mg/kg) or GnRH (100 micrograms/ewe). When averaged across all days and implant groups, serum LH in the three post-NAL samples was higher (P less than .05) than in the three pre-NAL samples (3.6 +/- 1.2 vs .6 +/- .2 ng/ml). Post-GnRH concentrations of serum LH were lower (P less than .05) in estradiol-implanted ewes than in non-implanted ewes on d 8 and 13, but there were no differences in any LH characteristics on d 20 and 28 after implant removal on d 12. In non-implanted ewes, serum LH responses to GnRH increased (P less than .05) eightfold from d 3 (3.8 +/- 1.4 ng/ml) to d 8 (31.6 +/- 1.4 ng/ml), remained elevated through d 20, but declined by d 28 (10.8 +/- 1.4 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)
Leakakos
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Hudgens
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Diekman
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Moss
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D000780:Anestrus / Q000187:drug effects; D000818:Animals; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology*; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D049590:Postpartum Period / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D012756:Sheep / Q000502:physiology*
D004343:Drug Implants; D010906:Pituitary Hormone-Releasing Hormones; D009270:Naloxone; D004958:Estradiol; D007986:Luteinizing Hormone