Regulation of circulating gonadotropins by the negative effects of ovarian hormones in mares.
Abstract: The functional and temporal relationships between circulating gonadotropins and ovarian hormones in mares during Days 7-27 (ovulation = Day 0) was studied using control, follicle ablation, and ovariectomy groups (n = 6 mares/group). In the follicle-ablation group, all follicles > or = 6 mm were ablated on Day 7, and every 2 days thereafter, newly emerging follicles were also ablated. Estradiol concentrations decreased (P < 0.01) similarly in the controls and the follicle-ablation group between Days 7 and 11 and by Day 15 began to increase in the controls and continued to decrease in the follicle-ablation group. Concentrations of progesterone were not affected by follicle ablation, but diameter of the corpus luteum was greater (P < 0.05) by Day 21 in the follicle-ablation group; these results indicated that the follicles were involved in morphologic luteolysis, but not in functional luteolysis. Concentrations of LH were higher (P < 0.05) on Days 15 and 16 in the follicle-ablation group than in the controls, indicating an initial negative effect of follicles on LH. Immunoreactive inhibin and estradiol decreased (P < 0.0001) and FSH and LH increased (P < 0.05) within 1 or 2 days after ovariectomy; these changes occurred more slowly in the follicle-ablation group. The maximum value for an FSH surge in each control mare was below the lower 95% confidence limit in the ovariectomy group. Maximum concentration for the periovulatory LH surge in the controls was not different from the mean maximum LH concentrations in the ovariectomy group. Our interpretation is that the gonadotropin surges resulted from changes in the magnitude of the negative effects of ovarian hormones on the positive effects of extraovarian control. There was no indication of a positive ovarian effect on either FSH or LH.
Publication Date: 2005-04-13 PubMed ID: 15829621DOI: 10.1095/biolreprod.105.040253Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research paper explores the relationship between circulating gonadotropins and ovarian hormones in mares during specific days of their reproductive cycle. The study found that follicles have an initial negative impact on luteinizing hormone levels and that inhibin and estradiol levels reduce while levels of follicle-stimulating hormone and LH increase after ovariectomy.
Study Design and Methodology
- The researchers carried out the study in mares from the 7th to the 27th day of their reproductive cycle, where ovulation is assigned Day 0.
- The study comprises control, follicle ablation, and ovariectomy groups, each having 6 mares. All follicles greater or equal to 6 mm were ablated on Day 7 and at every 2-day intervals afterwards in the follicle-ablation group.
Results and Findings
- Estradiol concentrations similarly decreased between Days 7 and 11 in both the controls and the follicle-ablation group, but began to increase in the control group and continued to decrease in the follicle-ablation group by Day 15.
- Progesterone concentrations were not affected by follicle ablation. However, the diameter of the corpus luteum was larger in the follicle-ablation group showing that follicles were involved in morphological luteolysis but not functional luteolysis.
- On Days 15 and 16, luteinizing hormone (LH) concentrations were higher in the follicle-ablation group than the controls, suggesting an initial negative effect of follicles on LH.
- After ovariectomy, immunoreactive inhibin and estradiol declined rapidly, while follicle-stimulating hormone (FSH) and LH witnessed a surge within 1 or 2 days. These changes occurred at a slower pace in the follicle-ablation group.
Conclusion
- The inference is that the surges of the gonadotropins resulted from the changes in the magnitude of the negative effects of ovarian hormones over the positive effects of extraovarian control.
- There was no sign of a positive ovarian effect on either FSH or LH.
Cite This Article
APA
Ginther OJ, Gastal EL, Gastal MO, Beg MA.
(2005).
Regulation of circulating gonadotropins by the negative effects of ovarian hormones in mares.
Biol Reprod, 73(2), 315-323.
https://doi.org/10.1095/biolreprod.105.040253 Publication
Researcher Affiliations
- Eutheria Foundation, Cross Plains, Wisconsin 53528, USA. ginther@svm.vetmed.wisc.edu
MeSH Terms
- Animals
- Estradiol / blood
- Female
- Follicle Stimulating Hormone / blood
- Horses / blood
- Inhibins / blood
- Luteinizing Hormone / blood
- Ovarian Follicle / metabolism
- Ovarian Follicle / surgery
- Ovariectomy / veterinary
- Ovulation / physiology
- Progesterone / blood
- Random Allocation
- Statistics, Nonparametric
- Time Factors
Citations
This article has been cited 7 times.- Satué K, Fazio E, La Fauci D, Medica P. Changes of Hepcidin, Ferritin and Iron Levels in Cycling Purebred Spanish Mares.. Animals (Basel) 2023 Mar 31;13(7).
- Goodman RL, Herbison AE, Lehman MN, Navarro VM. Neuroendocrine control of gonadotropin-releasing hormone: Pulsatile and surge modes of secretion.. J Neuroendocrinol 2022 May;34(5):e13094.
- Lin XH, Lass G, Kong LS, Wang H, Li XF, Huang HF, O'Byrne KT. Optogenetic Activation of Arcuate Kisspeptin Neurons Generates a Luteinizing Hormone Surge-Like Secretion in an Estradiol-Dependent Manner.. Front Endocrinol (Lausanne) 2021;12:775233.
- Ma L, Li Z, Ma Z, Ma J, Zhao F. Immunization Against Inhibin Promotes Fertility in Cattle: A Meta-Analysis and Quality Assessment.. Front Vet Sci 2021;8:687923.
- Montani DA, Braga DPAF, Borges E Jr, Camargo M, Cordeiro FB, Pilau EJ, Gozzo FC, Fraietta R, Lo Turco EG. Understanding mechanisms of oocyte development by follicular fluid lipidomics.. J Assist Reprod Genet 2019 May;36(5):1003-1011.
- Kozai K, Hojo T, Tokuyama S, Szóstek AZ, Takahashi M, Sakatani M, Nambo Y, Skarzynski DJ, Okuda K. Expression of aldo-keto reductase 1C23 in the equine corpus luteum in different luteal phases.. J Reprod Dev 2014 Apr 24;60(2):150-4.
- Lehman MN, Hileman SM, Goodman RL. Neuroanatomy of the kisspeptin signaling system in mammals: comparative and developmental aspects.. Adv Exp Med Biol 2013;784:27-62.
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