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Journal of animal science2018; 95(11); 5151-5160; doi: 10.2527/jas2017.1852

Tall fescue ergot alkaloids are vasoactive in equine vasculature.

Abstract: Mares grazing endophyte-infected () tall fescue () typically exhibit reproductive dysfunction rather than problems associated with peripheral vasoconstriction as a primary sign of the fescue toxicosis syndrome. Research using Doppler ultrasonography demonstrated that consumption of endophyte-infected tall fescue seed causes measurable vasoconstriction in the medial palmar artery. The objective of this study was to evaluate contractile responses of medial palmar artery and vein to increasing concentrations of various tall fescue alkaloids. Medial palmar arteries and veins were collected immediately following euthanasia from 23 horses of mixed breed, age, and gender from both forelimbs, and uterine arteries were collected from females ( = 12). Vessels were separated, cleaned of excess connective and adipose tissue, divided into 2- to 3-mm cross-sections, and suspended in a multimyograph chamber with continuously oxygenated Krebs-Henseleit buffer (95% O/5% CO; pH 7.4; 37°C). Following a 90-min equilibration and recovery from reference compound exposure, increasing concentrations of norepinephrine, 5-hydroxytryptamine, ergotamine, and ergonovine for the palmar artery and vein and uterine artery and ergovaline, ergocryptine, ergocristine, ergocornine, and lysergic acid for the palmar artery and vein were added to assess vasoactivity. Data were normalized as a percentage of contractile response induced by the reference compound addition and analyzed as a completely randomized design. Both norepinephrine and serotonin were vasoactive in all 3 types of blood vessels. Neither ergotamine nor ergonovine were vasoactive in the uterine artery. All alkaloids tested with the palmar artery and vein produced a contractile response, except that neither the palmar artery nor the palmar vein responded to lysergic acid ( > 0.05). Ergovaline was the most vasoactive ergot alkaloid in both the palmar artery and the palmar vein ( < 0.05) followed by ergonovine, whereas out of the 4 remaining ergopeptine alkaloids tested, ergocristine induced the lowest contractile response. Although horses do not outwardly appear to be affected by peripheral vasoconstriction as observed in cattle, these data indicate that tall fescue alkaloids are vasoactive and suggest that potential exists for peripheral vascular effects of tall fescue alkaloids in horses. This does not appear to be the case for the uterine artery, and future research should be directed at understanding how ergot alkaloids cause equine reproductive dysfunction.
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Publication Date: 2018-01-03 PubMed ID: 29293720PubMed Central: PMC6292298DOI: 10.2527/jas2017.1852Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research examines the impact of tall fescue alkaloids on the contraction of blood vessels in horses. The study establishes that these alkaloids significantly have a vasoactive effect, causing measurable vasoconstriction, especially in the equine palmar artery and vein.

Key Research Processes

  • The researchers sourced animals of mixed breed, age, and both genders for the study.
  • The medial palmar arteries and veins of the horses were collected immediately after euthanasia, and uterine arteries were collected from female horses.
  • The vessels were cleaned, divided into small cross-sections, and placed in a multimyograph chamber with Krebs-Henseleit buffer — a solution designed to mimic the environment inside living organisms.
  • After a stabilization period, the arteries and veins were exposed to increasing concentrations of various fescue alkaloids.

Key Findings

  • All types of blood vessels reacted to the presence of norepinephrine and serotonin, known to cause vasoconstriction or narrowing of the blood vessels.
  • The uterine artery did not react to ergotamine or ergonovine which are types of ergot alkaloids.
  • Nevertheless, all alkaloids tested stimulated a contractile response in the palmar artery and vein, with ergovaline being the most effective.
  • The palmar artery and vein did not react to lysergic acid, another form of alkaloids.

Implications and Conclusions

  • Although horses aren’t visibly affected by peripheral vasoconstriction like cattle, the research suggested that tall fescue alkaloids still have a considerable vasoactive effect on them.
  • However, the same effect was not observed in the uterine artery, suggesting that the alkaloids do not affect all blood vessels in the same way.
  • The findings indicate the potential for the alkaloids to cause peripheral vascular effects in horses.
  • Given that horses typically exhibit reproductive dysfunction due to fescue toxicosis rather than peripheral vasoconstriction, the researchers conclude that further research into how ergot alkaloids may cause reproductive dysfunction is needed.

Cite This Article

APA
Klotz JL, McDowell KJ. (2018). Tall fescue ergot alkaloids are vasoactive in equine vasculature. J Anim Sci, 95(11), 5151-5160. https://doi.org/10.2527/jas2017.1852

Publication

Journal of animal science
ISSN: 1525-3163
NlmUniqueID: 8003002
Country: United States
Language: English
Volume: 95
Issue: 11
Pages: 5151-5160

Researcher Affiliations

Klotz, J L
    McDowell, K J

      MeSH Terms

      • Animal Feed / analysis
      • Animals
      • Arteries / drug effects
      • Endophytes / chemistry
      • Endophytes / physiology
      • Ergot Alkaloids / chemistry
      • Ergot Alkaloids / pharmacology
      • Ergot Alkaloids / toxicity
      • Female
      • Festuca / chemistry
      • Festuca / microbiology
      • Horses / blood
      • Horses / physiology
      • Male
      • Uterine Artery / drug effects
      • Vasoconstriction / drug effects
      • Vasoconstrictor Agents / chemistry
      • Vasoconstrictor Agents / pharmacology
      • Vasoconstrictor Agents / toxicity
      • Veins / drug effects

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      Citations

      This article has been cited 8 times.
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      2. Lea KM, Smith SR. Using On-Farm Monitoring of Ergovaline and Tall Fescue Composition for Horse Pasture Management. Toxins (Basel) 2021 Sep 25;13(10).
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      4. Poole RK, Poole DH. Impact of Ergot Alkaloids on Female Reproduction in Domestic Livestock Species. Toxins (Basel) 2019 Jun 21;11(6).
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