Journal of applied physiology (Bethesda, Md. : 1985)2001; 91(2); 891-896; doi: 10.1152/jappl.2001.91.2.891

Effect of L-NAME on oxygen uptake kinetics during heavy-intensity exercise in the horse.

Abstract: There is evidence that oxidative enzyme inertia plays a major role in limiting/setting the O(2) uptake (VO(2)) response at the transition to higher metabolic rates and also that nitric oxide (NO) competitively inhibits VO(2) within the electron transport chain. To investigate whether NO is important in setting the dynamic response of VO(2) at the onset of high-intensity (heavy-domain) running in horses, five geldings were run on a treadmill across speed transitions from 3 m/s to speeds corresponding to 80% of peak VO(2) with and without nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor (20 mg/kg; order randomized). L-NAME did not alter (both P > 0.05) baseline (3 m/s, 15.4 +/- 0.3 and 16.2 +/- 0.5 l/min for control and L-NAME, respectively) or end-exercise VO(2) (56.9 +/- 5.1 and 55.2 +/- 5.8 l/min for control and L-NAME, respectively). However, in the L-NAME trial, the primary on-kinetic response was significantly (P 0.05). The faster on-kinetic response was confirmed independent of modeling by reduced time to 50, 63, and 75% of overall VO(2) response (all P < 0.05). In addition, onset of the VO(2) slow component occurred earlier (124.6 +/- 11.2 and 65.0 +/- 6.6 s for control and L-NAME, respectively), and the magnitude of the O(2) deficit was attenuated (both P < 0.05) in the L-NAME compared with the control trial. Acceleration of the VO(2) kinetics by L-NAME suggests that NO inhibition of mitochondrial VO(2) may contribute, in part, to the intrinsic metabolic inertia evidenced at the transition to higher metabolic rates in the horse.
Publication Date: 2001-07-18 PubMed ID: 11457807DOI: 10.1152/jappl.2001.91.2.891Google Scholar: Lookup
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  • Journal Article
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  • Non-U.S. Gov't
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  • U.S. Gov't
  • P.H.S.

Summary

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The research study aimed to investigate how L-NAME (a nitric oxide synthase inhibitor) affects a horse’s oxygen consumption during high-intensity exercise. It found that although L-NAME did not alter the baseline or end-exercise oxygen uptake, it significantly sped up the primary on-kinetic response, suggesting that the inhibition of mitochondrial oxygen uptake by nitric oxide could be contributing to the metabolic inertia observed when horses transition to higher metabolic rates.

Research Context

  • This study focuses on understanding how Nitric Oxide (NO), a gas produced in the body that has several important functions including regulating blood pressure and assisting the immune system, intrinsically affects oxygen uptake.
  • The researchers used L-NAME (nitro-L-arginine methyl ester), an inhibitor of Nitric Oxide Synthase (NOS), the enzyme responsible for creating NO in the body.
  • The goal was to investigate whether NO plays a significant role in setting the dynamic response of oxygen uptake (VO2) during heavy-intensity exercise in horses.

Experimental Design and Results

  • Five geldings (castrated male horses) were made to run on a treadmill at different intensities, with and without the administration of L-NAME.
  • The experiments controlled for speed, moving from 3 m/s to speeds that corresponded to 80% of their peak oxygen uptake.
  • The study found that L-NAME did not alter either the baseline or end-exercise oxygen uptake levels.
  • Despite this, the primary on-kinetic response – the oxygen uptake response triggered at the onset of heavy-intensity running – was significantly faster in the L-NAME trial.
  • The onset of the VO2 slow component occurred earlier with L-NAME and the magnitude of the oxygen deficit was also reduced compared to the control trial.

Research implications

  • By finding that L-NAME accelerates the VO2 kinetics, the study provides evidence that Nitric Oxide plays a part in the inertia of metabolic responses when a horse transitions to high-intensity exercise.
  • Further work is needed to investigate this effect across different species and to further understand the mechanisms by which Nitric Oxide affects VO2 kinetics.

Cite This Article

APA
Kindig CA, McDonough P, Erickson HH, Poole DC. (2001). Effect of L-NAME on oxygen uptake kinetics during heavy-intensity exercise in the horse. J Appl Physiol (1985), 91(2), 891-896. https://doi.org/10.1152/jappl.2001.91.2.891

Publication

ISSN: 8750-7587
NlmUniqueID: 8502536
Country: United States
Language: English
Volume: 91
Issue: 2
Pages: 891-896

Researcher Affiliations

Kindig, C A
  • Department of Anatomy, Kansas State University, Manhattan, Kansas 66506-5602, USA.
McDonough, P
    Erickson, H H
      Poole, D C

        MeSH Terms

        • Animals
        • Carbon Dioxide / analysis
        • Horses
        • Kinetics
        • Male
        • Mass Spectrometry
        • NG-Nitroarginine Methyl Ester / pharmacology
        • Orchiectomy
        • Oxygen / analysis
        • Oxygen Consumption / drug effects
        • Physical Conditioning, Animal / physiology
        • Physical Exertion / drug effects
        • Physical Exertion / physiology
        • Respiratory Mechanics / physiology
        • Time Factors

        Grant Funding

        • HL-50306 / NHLBI NIH HHS

        Citations

        This article has been cited 17 times.
        1. 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.
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        11. Haseler LJ, Kindig CA, Richardson RS, Hogan MC. The role of oxygen in determining phosphocreatine onset kinetics in exercising humans.. J Physiol 2004 Aug 1;558(Pt 3):985-92.
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        13. Jones AM, Koppo K, Wilkerson DP, Wilmshurst S, Campbell IT. Dichloroacetate does not speed phase-II pulmonary VO2 kinetics following the onset of heavy intensity cycle exercise.. Pflugers Arch 2004 Mar;447(6):867-74.
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        14. Jones AM, Koppo K, Burnley M. Effects of prior exercise on metabolic and gas exchange responses to exercise.. Sports Med 2003;33(13):949-71.
        15. Grassi B. Oxygen uptake kinetics: old and recent lessons from experiments on isolated muscle in situ.. Eur J Appl Physiol 2003 Oct;90(3-4):242-9.
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        16. Jones AM, Wilkerson DP, Koppo K, Wilmshurst S, Campbell IT. Inhibition of nitric oxide synthase by L-NAME speeds phase II pulmonary .VO2 kinetics in the transition to moderate-intensity exercise in man.. J Physiol 2003 Oct 1;552(Pt 1):265-72.
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        17. Pringle JS, Doust JH, Carter H, Tolfrey K, Campbell IT, Sakkas GK, Jones AM. Oxygen uptake kinetics during moderate, heavy and severe intensity "submaximal" exercise in humans: the influence of muscle fibre type and capillarisation.. Eur J Appl Physiol 2003 May;89(3-4):289-300.
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