Response of estradiol and inhibin to experimentally reduced luteinizing hormone during follicle deviation in mares.
Abstract: The increase in LH concentrations at the time of the decrease in FSH concentrations during follicle deviation in mares was studied to determine the role of LH in the production of estradiol and immunoreactive inhibin (ir-inhibin). Ten days after ovulation, all follicles > or =6 mm were ablated, prostaglandin F(2 alpha) was given, and either 0 mg (control group, n = 15) or 100 mg of progesterone in safflower oil (treated group, n = 16) was given daily for 14 days, encompassing the day of diameter deviation. The follicular and hormonal data were normalized to the expected day of the beginning of diameter deviation when the largest follicle first reached > or =20 mm (Day 0). The experimentally induced decrease in LH concentrations during follicle deviation beginning on Day -4 delayed and stunted the increase in circulating concentrations of ir-inhibin and estradiol beginning on Days -3 and -1, respectively, but did not alter the predeviation FSH surge and the initiation of diameter deviation between the two largest follicles. Combined for both groups, the interval to the expected day of deviation was 16.6 days after ovulation when the largest follicle was a mean of 21.6 mm. After deviation, the largest follicle started to regress in the treated group beginning on Day 1 and was associated with decreased concentrations of ir-inhibin and estradiol, and increased concentrations of FSH. The negative influence of the dominant follicle on the postdeviation decrease in FSH observed in the control group was alleviated and concentrations resurged in the treated group. Apparently this is the first in vivo evidence that the increase in LH that precedes follicle deviation has a positive effect in supporting the production of inhibin during diameter deviation. It was concluded that the increase in LH concentrations before diameter deviation played a role in the production of estradiol and inhibin by the largest follicle during deviation.
Publication Date: 2001-07-24 PubMed ID: 11466210DOI: 10.1095/biolreprod65.2.426Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study investigates the role of luteinizing hormone (LH) on the production of estradiol and inhibin during the process of follicle deviation in mares. Lower LH levels appeared to delay and limit the rise of estradiol and inhibin, but didn’t affect the follicle-stimulating hormone (FSH) levels prior to deviation.
Objective and Methodology
- The research aimed at understanding the role luteinizing hormone (LH) plays in the production of estradiol and inhibin, which are key players in the reproductive process in mares.
- Two groups of mares were used for the experiment, a control group with normal levels of LH and a treated group whose LH was manipulated using progesterone in safflower oil.
- The mares’ follicles were ablated ten days after ovulation, and their hormonal data was assessed beginning from the day of diameter deviation (Day 0), when the largest follicle reached or exceeded 20mm.
Findings
- Lower LH levels in the treated group delayed the increase in the circulating concentrations of immunoreactive inhibin and estradiol, two hormones that are vital for the reproductive cycle.
- However, the reduction in LH did not affect the predeviation surge of follicle-stimulating hormone (FSH) and the diameter deviation initiation of two largest follicles.
- While LH levels did not influence the initial steps of diameter deviation, they appear critical for the normal progression of the process, especially in producing estradiol and inhibin.
Conclusion
- The research concluded that increased LH levels prior to follicle diameter deviation positively supported the production of inhibin and were involved in the production of estradiol by the largest follicle.
- Lowering LH concentrations therefore seems to impact the reproductive process in mares, underlining the importance of LH levels during follicle deviation.
- This study provides the first in vivo evidence for the positive effect of LH in supporting inhibin production during follicle deviation.
Cite This Article
APA
Bergfelt DR, Gastal EL, Ginther OJ.
(2001).
Response of estradiol and inhibin to experimentally reduced luteinizing hormone during follicle deviation in mares.
Biol Reprod, 65(2), 426-432.
https://doi.org/10.1095/biolreprod65.2.426 Publication
Researcher Affiliations
- Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, Wisconsin 53706, USA. drb@ahabs.wisc.edu
MeSH Terms
- Animals
- Dinoprost / administration & dosage
- Dinoprost / pharmacology
- Estradiol / blood
- Female
- Follicle Stimulating Hormone / blood
- Horses / physiology
- Inhibins / blood
- Kinetics
- Luteinizing Hormone / blood
- Ovarian Follicle / anatomy & histology
- Ovarian Follicle / physiology
- Progesterone / administration & dosage
- Progesterone / pharmacology
Citations
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