Negative effect of estradiol on luteinizing hormone throughout the ovulatory luteinizing hormone surge in mares.
Abstract: The negative effect of estradiol-17beta (E2) on LH, based on exogenous E2 treatments, and the reciprocal effect of LH on endogenous E2, based on hCG treatments, were studied throughout the ovulatory follicular wave during a total of 103 equine estrous cycles in seven experiments. An initial study developed E2 treatment protocols that approximated physiologic E2 concentrations during the estrous cycle. On Day 13 (ovulation = Day 0), when basal concentrations of E2 and LH precede the ovulatory surges, exogenous E2 significantly depressed LH concentrations to below basal levels. Ablation of all follicles > or = 10 mm when the largest was > or =20 mm resulted in an increase in percentage change in LH concentration within 8 h that was greater (P or =25 mm, > or =28 mm, > or =35 mm, or near ovulation. Treatment with 200 or 2000 IU of hCG did not affect E2 concentrations during the initial portion of the LH surge (largest follicle, > or =25 mm), but 2000 IU significantly depressed E2 concentrations before ovulation (largest follicle, > or =35 mm). Results indicated a continuous negative effect of E2 on LH throughout the ovulatory follicular wave and may be related to the long LH surge and the long follicular phase in mares. Results also indicated that a reciprocal negative effect of LH on E2 does not develop until the E2 surge reaches a peak.
Publication Date: 2007-06-06 PubMed ID: 17554078DOI: 10.1095/biolreprod.107.061705Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study investigates the impact of a hormone, estradiol-17beta (E2), on luteinizing hormone (LH) during the ovulatory cycle in mares, based on external E2 treatments and how LH affects internal E2 following hCG treatments.
Summary of Study
- This research spanned across a total of 103 equine estrous cycles in seven distinct experiments. The researchers closely studied the reverse effect of the luteinizing hormone (LH) on endogenous estradiol-17beta (E2), and vice versa.
- Initial trials aimed to develop E2 treatment protocols that would closely resemble the natural E2 concentrations during the estrous cycle.
- On Day 13 of the cycle (with ovulation defined as Day 0), treatment with exogenous E2 considerably reduced LH concentrations below their base levels at a time when basal levels of E2 and LH typically precede ovulatory surges.
Follicle Ablation and Resultant Changes
- Removing all follicles greater than or equal to 10mm when the largest one was larger than or equal to 20mm resulted in an increase in percentage of change in LH concentration within 8 hours. This increase was significantly higher than the changes in control cases or E2-treated mares that had undergone follicle ablation.
- Notable decreases in LH concentration were recorded when E2 was administered when the largest follicle was either bigger than or equal to 25mm, 28mm, 35mm, or nearing ovulation.
Effects of hCG Treatment
- Administering 200 or 2000 IU of human chorionic gonadotropin (hCG) did not considerably change E2 concentrations during the opening phase of the LH surge (when the largest follicle was at least 25mm).
- However, a dose of 2000 IU of hCG significantly diminished E2 concentrations before ovulation (when the largest follicle was at least 35mm).
Conclusion of Research
- The study evidenced a persistent negative influence of E2 on LH throughout the ovulatory follicular wave in horses. This might be related to the extended LH surge and the long follicular phase seen in mares.
- The findings also suggested that a reciprocal negative impact of LH on E2 does not become evident until the E2 surge reaches its peak.
Cite This Article
APA
Ginther OJ, Utt MD, Beg MA, Gastal EL, Gastal MO.
(2007).
Negative effect of estradiol on luteinizing hormone throughout the ovulatory luteinizing hormone surge in mares.
Biol Reprod, 77(3), 543-550.
https://doi.org/10.1095/biolreprod.107.061705 Publication
Researcher Affiliations
- Eutheria Foundation, Cross Plains, Wisconsin 53528, USA. ginther@svm.vetmed.wisc.edu
MeSH Terms
- Animals
- Chorionic Gonadotropin / pharmacology
- Chorionic Gonadotropin / physiology
- Estradiol / blood
- Estradiol / pharmacology
- Estrous Cycle / drug effects
- Estrous Cycle / physiology
- Female
- Horses / physiology
- Luteinizing Hormone / blood
- Ovarian Follicle / drug effects
- Ovarian Follicle / physiology
- Time Factors
Citations
This article has been cited 1 times.- Nagy AM, Abdelhameed MF, Elkarim ASA, Sarker TC, Abd-ElGawad AM, Elshamy AI, Hammam AM. Enhancement of Female Rat Fertility via Ethanolic Extract from Nigella sativa L. (Black Cumin) Seeds Assessed via HPLC-ESI-MS/MS and Molecular Docking. Molecules 2024 Feb 5;29(3).
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