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Journal of muscle research and cell motility2003; 24(7); 471-476; doi: 10.1023/a:1027377731137

Therapeutic clenbuterol treatment does not alter Ca2+ sensitivity of permeabilized fast muscle fibres from exercise trained or untrained horses.

Abstract: Clenbuterol is a beta2-adrenoceptor agonist primarily used for treating bronchospasm and alleviating the symptoms of chronic obstructive pulmonary disease (COPD) in the horse. In other species (rats, mice, sheep, and cattle), chronic high doses of clenbuterol (typically in the milligram per kilogram body weight range) has been shown to cause a muscle directed protein anabolic response. Clenbuterol can also modify muscle fibre composition and therefore potentially affect muscle function. This has implications for the performance of exercising horses being treated with therapeutic doses of clenbuterol (typically in the microgram per kilogram body weight range) for bronchospasm or COPD. It is not known whether clenbuterol treatment affects muscle fibre function in horses. The purpose of this study was to examine the effects of a therapeutic dose of clenbuterol, with and without exercise, on the contractile activation characteristics of single membrane permeabilized fibres prepared from muscle biopsies. We tested the hypothesis that therapeutic treatment with clenbuterol would not affect muscle fibre function. Unfit Standardbred mares were treated for 8 weeks with; clenbuterol (2.4 microg/kg twice/day, 5 days/week) plus exercise (20 min at 50% VO2(max) 3 d/wk; CLENEX), clenbuterol only (CLEN), or exercise only (EX). Muscle biopsies were taken from the gluteus medius muscle before and after treatment and stored in a glycerol-based solution to prepare permeabilized muscle fibres. The force-pCa relationship for fibres from CLEN horses was steeper (P < 0.05) indicative of greater cooperative interactions within the thin filament, however, fibre sensitivity to Ca2+ was unchanged. In contrast, the steepness of the force-pCa relationship was not changed in fibres from EX and CLENEX horses and Ca2+ sensitivity was also unaffected. Rigor force, activation in the absence of ATP, was not affected by any treatment indicating an approximately equivalent number of participating cross-bridges during activation. The results indicate that a therapeutic dose of clenbuterol to Standardbred horses does not affect the Ca(2+)-activated contractile characteristics of isolated muscle fibres.
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Publication Date: 2003-12-18 PubMed ID: 14677650DOI: 10.1023/a:1027377731137Google Scholar: Lookup
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  • 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.

The research article investigates whether a therapeutic dose of clenbuterol, a medication primarily used to treat breathing disorders in horses, affects the function of muscle fibres in these animals, both with and without exercise. The findings show that the medication, in therapeutic amounts, does not alter calcium-activated contractile characteristics in the muscle fibres of these horses.

Objective of the Research

The study seeks to understand the impact of clenbuterol on muscle fibre function in horses. Clenbuterol, a beta2-adrenoceptor agonist, has been shown in other species to cause an anabolic response in muscles with high doses. This could potentially impact muscle composition and function, affecting the performance of horses treated with the medication for bronchospasm or chronic obstructive pulmonary disease (COPD). Considering these implications, the researchers hypothesize that therapeutic doses of clenbuterol would not affect the function of the muscle fibres of horses.

  • The therapeutic dosage used was 2.4 micrograms/kg twice per day, five days a week, over an eight-week period.
  • The study also considered the potential impact of exercise on the outcomes, utilizing a regimen of 20 minutes at 50% VO2max, three times per week.
  • Muscle biopsies, taken from the gluteus medius muscle before and after treatment, were used to examine the impact on muscle fibres.

Findings of the Research

The study found that therapeutic doses of clenbuterol do not impact the calcium-activated contractile characteristics of horse muscle fibres.

  • In horses treated solely with clenbuterol (CLEN group), the force and calcium relationship was steeper, indicating more cooperative interactions within the thin filament. However, fibre sensitivity to calcium remained unchanged.
  • Contrastingly, in horses treated with clenbuterol and subjected to exercise (CLENEX group), as well as those subjected to exercise alone (EX group), the steepness of the force and calcium relationship exhibited no change. Similarly, calcium sensitivity also remained unchanged.
  • In all groups, rigor force, activation in the absence of ATP, remained unaffected. This suggests an approximately equivalent number of participating cross-bridges during activation.

Conclusion of the Research

These findings led the researchers to conclude that therapeutic doses of clenbuterol do not affect the calcium-activated contractile characteristics of muscle fibres in horses. This suggests that the administration of clenbuterol for bronchospasm or COPD treatment wouldn’t adversely impact the muscle performance of horses.

Cite This Article

APA
Plant DR, Kearns CF, McKeever KH, Lynch GS. (2003). Therapeutic clenbuterol treatment does not alter Ca2+ sensitivity of permeabilized fast muscle fibres from exercise trained or untrained horses. J Muscle Res Cell Motil, 24(7), 471-476. https://doi.org/10.1023/a:1027377731137

Publication

Journal of muscle research and cell motility
ISSN: 0142-4319
NlmUniqueID: 8006298
Country: Netherlands
Language: English
Volume: 24
Issue: 7
Pages: 471-476

Researcher Affiliations

Plant, David R
  • Department of Physiology, The University of Melbourne, Victoria 3010, Australia.
Kearns, Charles F
    McKeever, Kenneth H
      Lynch, Gordon S

        MeSH Terms

        • Adrenergic beta-Agonists / pharmacology
        • Animals
        • Calcium / metabolism
        • Clenbuterol / pharmacology
        • Horses / metabolism
        • Horses / physiology
        • Male
        • Muscle Contraction / physiology
        • Muscle Fibers, Skeletal / drug effects
        • Muscle Fibers, Skeletal / metabolism
        • Muscle Fibers, Skeletal / physiology
        • Muscle, Skeletal / drug effects
        • Muscle, Skeletal / metabolism
        • Muscle, Skeletal / physiology
        • Physical Conditioning, Animal

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        Citations

        This article has been cited 5 times.
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        2. Koeberl DD, Li S, Dai J, Thurberg BL, Bali D, Kishnani PS. β2 Agonists enhance the efficacy of simultaneous enzyme replacement therapy in murine Pompe disease. Mol Genet Metab 2012 Feb;105(2):221-7.
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        3. Koeberl DD, Luo X, Sun B, McVie-Wylie A, Dai J, Li S, Banugaria SG, Chen YT, Bali DS. Enhanced efficacy of enzyme replacement therapy in Pompe disease through mannose-6-phosphate receptor expression in skeletal muscle. Mol Genet Metab 2011 Jun;103(2):107-12.
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