Changes in serum concentrations of luteinizing hormone and follicle-stimulating hormone following injection of gonadotropin-releasing hormone during pregnancy and after parturition in mares.
Abstract: High concentrations of estrogens in the peripheral circulation during late gestation inhibit synthesis of LH and markedly reduce pituitary content of LH at the end of pregnancy in most domestic species. Because blood concentrations of estrogen peak shortly before mid-gestation in the mare and then gradually decrease until parturition, we hypothesized that pituitary content of LH may increase during late gestation. To test this hypothesis 10 horse mares were challenged with a maximally stimulatory dose (2 micrograms/kg) of GnRH on d 240 and 320 of gestation and d 3 after parturition. A separate group of four mares were treated with GnRH on d 2 or 3 estrus. Blood samples were collected at -2, -1, 0, .25, .5, .75, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7 and 8 h relative to injection of GnRH and serum was analyzed for concentration of LH and FSH. Basal serum concentration and total quantity of LH released after GnRH stimulation (assessed by determining the area under the response curve) were not different on d 240 and 320 of gestation or on d 3 after parturition (12.5 +/- 3.5, 5.7 +/- 1.5 and 29.1 +/- 12.1 ng.min/ml, respectively) and were less (P less than .05) than on d 3 of estrus (311.0 +/- 54.0 ng.min/ml). There was little difference in the basal serum concentration of FSH at any of the time points examined. In contrast, GnRH-induced release of FSH continually decreased (P less than .05) from d 240 of gestation (559.8 +/- 88.9 ng.min/ml) to d 3 of estrus (51.8 +/- 6.2 ng.min/ml).(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1989-05-01 PubMed ID: 2500415DOI: 10.2527/jas1989.6751330xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The article investigates the changes in the concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in mares following the injection of gonadotropin-releasing hormone (GnRH) during and after pregnancy.
Research Design and Methodology
- The research aimed to test the hypothesis that pituitary content of LH may increase in mares during late pregnancy, given the decrease in blood concentrations of estrogen from mid-gestation to parturition.
- The experiment involved 10 mare horses who were injected with a high dose of GnRH on day 240 and 320 of gestation and day three post-parturition.
- Another group of four mares were treated with GnRH during estrus (on day two or three).
- After the GnRH injection, blood samples were collected at regular intervals to measure the concentration of LH and FSH in the serum.
Key Findings
- There was no significant difference in the basal serum concentration and total quantity of LH released after GnRH stimulation at the end of gestation or after parturition. However, these levels were markedly lower than those recorded on day three of estrus.
- On the other hand, there was minimal difference observed in the basal serum concentration of FSH at any point during the experiment.
- The GnRH-induced release of FSH continually decreased from day 240 of gestation to day three of estrus.
Significance of the Research
- This study offers insights into the hormonal changes in mares during late pregnancy and after parturition, which could be useful for better understanding the reproductive processes of these animals and the impact of hormonal treatments like GnRH.
- The research also presents findings that could be coupled with further research to improve strategies for managing mare reproduction and health.
Cite This Article
APA
Nett TM, Shoemaker CF, Squires EL.
(1989).
Changes in serum concentrations of luteinizing hormone and follicle-stimulating hormone following injection of gonadotropin-releasing hormone during pregnancy and after parturition in mares.
J Anim Sci, 67(5), 1330-1333.
https://doi.org/10.2527/jas1989.6751330x Publication
Researcher Affiliations
- Dept. of Physiol, Colorado State University, Fort Collins 80523.
MeSH Terms
- Animals
- Estrus / drug effects
- Estrus / metabolism
- Female
- Follicle Stimulating Hormone / blood
- Horses / blood
- Labor, Obstetric / blood
- Labor, Obstetric / drug effects
- Luteinizing Hormone / blood
- Pituitary Hormone-Releasing Hormones / pharmacology
- Pregnancy
- Pregnancy, Animal / blood
- Pregnancy, Animal / drug effects
Citations
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