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Home / Equine Research Bank / J Appl Physiol (1985) / Nitric oxide and thermoregulation during exercise in the hor...
Journal of applied physiology (Bethesda, Md. : 1985)1997; 82(4); 1035-1039; doi: 10.1152/jappl.1997.82.4.1035

Nitric oxide and thermoregulation during exercise in the horse.

Abstract: The effect of inhibition of nitric oxide production on sweating rate (SR) and on core, rectal, and tail skin temperatures was measured in five Thoroughbred horses during exercise of variable intensity on a high-speed treadmill. A standard exercise test consisting of three canters [approximately 55% maximum O2 uptake (VO2max)], with walking (approximately 9% VO2max) and trotting (approximately 22% VO2max) between each canter, was performed twice (control or test), in random order, by each horse. N(G)-nitro-L-arginine methyl ester (L-NAME; 20 mg/kg), a competitive inhibitor of nitric oxide synthase, was infused into the central circulation and induced a significant reduction in the SR measured on the neck (31.6 +/- 6.4 vs. 9.7 +/- 4.2 g x min(1) x m(-2); 69%) and rump (14.7 +/- 5.2 vs. 4.8 +/- 1.6 g x min(-1) x m(-2); 67%) of the horses during canter (P < 0.05). Significant increases in core, rectal, and tail skin temperatures were also measured (P < 0.05). L-Arginine (200 mg/kg iv) partially reversed the inhibitory effects of L-NAME on SR, but core, rectal, and tail skin temperatures continued to increase (P < 0.05), suggesting a cumulation of body heat. The results support the contention that nitric oxide synthase inhibition diminishes SR, resulting in elevated core and peripheral temperatures leading to deranged thermoregulation during exercise. The inhibition of sweating by L-NAME may be related to peripheral vasoconstriction but may also involve the neurogenic control of sweating.
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Publication Date: 1997-04-01 PubMed ID: 9104835DOI: 10.1152/jappl.1997.82.4.1035Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

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.

This research investigates how the inhibition of nitric oxide production affects heat regulation in horses during exercise. The main finding is that blocking nitric oxide production increases core and peripheral body temperatures, suggesting it plays a key role in maintaining body temperature.

Research Context and Methodology

  • The study was conducted on five Thoroughbred horses, where their capacity to regulate their body heat while exercising on a high-speed treadmill was measured.
  • The exercise regime consisted of three stints of canters, with walking and trotting interspersed. This was done twice, once under normal conditions (control) and one where nitric oxide production was inhibited (test), in a random order.
  • Nitric oxide production was inhibited by the infusion of N(G)-nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of nitric oxide synthase, directly into the central circulation of the horses.

Findings

  • Blocking nitric oxide production led to a marked decrease in Sweating Rate (SR), measured at the neck and the rump of the horses, during the canter phase of the exercise.
  • Simultaneously, significant increases in the core, rectal, and tail skin temperatures of the horses were also observed.
  • L-Arginine, an amino acid that reverses the inhibitory effects of L-NAME, was able to partially restore the Sweat Rate. However, the elevated body temperatures persisted, suggesting the accumulation of body heat.

Implications

  • The findings suggest that inhibiting the production of nitric oxide adversely affects the ability of a horse to regulate body heat during exercise.
  • This hindrance is likely due to the reduced sweating—which aids in heat dissipation—caused by the inhibition of nitric oxide production.
  • The study proposes two possible mechanisms for this: peripheral vasoconstriction, i.e., the narrowing of blood vessels, and alterations to the neurogenic control of sweating.
  • Overall, the results indicate that nitric oxide plays a crucial role in thermoregulation during physical activity in horses.

Cite This Article

APA
Mills PC, Marlin DJ, Scott CM, Smith NC. (1997). Nitric oxide and thermoregulation during exercise in the horse. J Appl Physiol (1985), 82(4), 1035-1039. https://doi.org/10.1152/jappl.1997.82.4.1035

Publication

Journal of applied physiology (Bethesda, Md. : 1985)
ISSN: 8750-7587
NlmUniqueID: 8502536
Country: United States
Language: English
Volume: 82
Issue: 4
Pages: 1035-1039

Researcher Affiliations

Mills, P C
  • Equine Centre, The Animal Health Trust, Newmarket, Suffolk, United Kingdom.
Marlin, D J
    Scott, C M
      Smith, N C

        MeSH Terms

        • Animals
        • Arginine / pharmacology
        • Body Temperature Regulation / physiology
        • Enzyme Inhibitors / pharmacology
        • Exercise Test
        • Female
        • Horses / physiology
        • Male
        • NG-Nitroarginine Methyl Ester / pharmacology
        • Nitric Oxide / physiology
        • Nitric Oxide Synthase / antagonists & inhibitors
        • Oxygen Consumption / drug effects
        • Oxygen Consumption / physiology
        • Physical Exertion / physiology
        • Skin Physiological Phenomena
        • Sweating / physiology

        Citations

        This article has been cited 6 times.
        1. Bukhari SSUH, McElligott AG, Parkes RSV. Quantifying the Impact of Mounted Load Carrying on Equids: A Review.. Animals (Basel) 2021 May 7;11(5).
          doi: 10.3390/ani11051333pubmed: 34067208google scholar: lookup
        2. Poole DC, Copp SW, Colburn TD, Craig JC, Allen DL, Sturek M, O'Leary DS, Zucker IH, Musch TI. Guidelines for animal exercise and training protocols for cardiovascular studies.. Am J Physiol Heart Circ Physiol 2020 May 1;318(5):H1100-H1138.
          doi: 10.1152/ajpheart.00697.2019pubmed: 32196357google scholar: lookup
        3. Tyler CJ, Coffey TR, Hodges GJ. Acute L-arginine supplementation has no effect on cardiovascular or thermoregulatory responses to rest, exercise, and recovery in the heat.. Eur J Appl Physiol 2016 Feb;116(2):363-71.
          doi: 10.1007/s00421-015-3295-5pubmed: 26563117google scholar: lookup
        4. Wingo JE, Low DA, Keller DM, Brothers RM, Shibasaki M, Crandall CG. Skin blood flow and local temperature independently modify sweat rate during passive heat stress in humans.. J Appl Physiol (1985) 2010 Nov;109(5):1301-6.
          doi: 10.1152/japplphysiol.00646.2010pubmed: 20705945google scholar: lookup
        5. Hubing KA, Wingo JE, Brothers RM, Del Coso J, Low DA, Crandall CG. Nitric oxide synthase inhibition attenuates cutaneous vasodilation during postmenopausal hot flash episodes.. Menopause 2010 Sep-Oct;17(5):978-82.
          doi: 10.1097/gme.0b013e3181d674d6pubmed: 20505548google scholar: lookup
        6. Njoku CJ, Saville WJ, Reed SM, Oglesbee MJ, Rajala-Schultz PJ, Stich RW. Reduced levels of nitric oxide metabolites in cerebrospinal fluid are associated with equine protozoal myeloencephalitis.. Clin Diagn Lab Immunol 2002 May;9(3):605-10.
          doi: 10.1128/cdli.9.3.605-610.2002pubmed: 11986267google scholar: lookup
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