NDLI: Effect of an estrogen antagonist (tamoxifen) on cloprostenol-induced luteolysis in heifers.

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Effect of an estrogen antagonist (tamoxifen) on cloprostenol-induced luteolysis in heifers.

Content Provider	Semantic Scholar
Author	Jacobs, Allison
Copyright Year	1988
Abstract	Experiments were conducted to determine the role of estrogens on endogenous PGF2 alpha secretion and luteolysis following injection of cloprostenol in heifers. In Exp. 1, eight luteal-phase heifers were used to evaluate tamoxifen (T) as an estrogen antagonist. Heifers received T (35 mg i.v.) or ethanol:saline vehicle (ES) every 4 h for 44 h. All received cloprostenol (500 micrograms i.m.) immediately after the start of T or ES, and received estradiol-17 beta (500 micrograms i.m.) 12 h later. Each ES heifer had a surge of luteinizing hormone (LH) within 48 h of estradiol injection, whereas T-treated heifers did not. Estrus was observed in three ES-treated heifers, but not in T-treated heifers. In Exp. 2, 10 heifers received T (35 mg i.v.) or ES every 4 h for 64 h beginning on d 15 postestrus. Cloprostenol (500 micrograms i.m.) was injected 16 h after the start of treatment. Concentrations of LH were similar (P greater than .05) in both groups. In ES heifers, concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) increased; in T-treated heifers, PGFM remained at pre-cloprostenol levels. Luteolysis was induced in all heifers. Progesterone (P4) decreased to less than or equal to 1 ng/ml at similar (P greater than .05) rates in ES-treated and T-treated heifers. Mean concentration of P4 288 h post-cloprostenol was greater (P less than .05) in ES-treated than in T-treated heifers. Three ES-treated heifers, but no T-treated heifers, were in standing estrus. We conclude that T effectively antagonizes estrogen in cattle.(ABSTRACT TRUNCATED AT 250 WORDS)
File Format	PDF HTM / HTML
Alternate Webpage(s)	https://www.animalsciencepublications.org/publications/jas/pdfs/66/3/JAN0660030735
PubMed reference number	3163991v1
Volume Number	66
Issue Number	3
Journal	Journal of animal science
Language	English
Access Restriction	Open
Subject Keyword	15-keto-13,14-dihydroprostaglandin F2alpha Adrenergic alpha-Agonists Cloprostenol Dinoprost Estradiol Estrogen Antagonists Estrogens Estrus Ethanol Gonadorelin Luteolysis Microgram per Liter Progesterone Prostaglandins Tamoxifen
Content Type	Text
Resource Type	Article

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