title: Effects of beta(2)-agonist clenbuterol on biochemical and contractile properties of unloaded soleus fibers of rat.
abstract: The effects of clenbuterol beta(2)-agonist administration were investigated in normal and atrophied [15-day hindlimb-unloaded (HU)] rat soleus muscles. We showed that clenbuterol had a specific effect on muscle tissue, since it reduces soleus atrophy induced by HU. The study of Ca(2+) activation properties of single skinned fibers revealed that clenbuterol partly prevented the decrease in maximal tension after HU, with a preferential effect on fast-twitch fibers. Clenbuterol improved the Ca(2+) sensitivity in slow- and fast-twitch fibers by shifting the tension-pCa relationship toward lower Ca(2+) concentrations, but this effect was more marked after HU than in normal conditions. Whole muscle electrophoresis indicated slow-to-fast transitions of the myosin heavy chain isoforms for unloaded and for clenbuterol-treated soleus. The coupling of the two latter conditions did not, however, increase these phenotypical transformations. Our findings indicated that clenbuterol had an anabolic action and a beta(2)-adrenergic effect on muscle fibers and appeared to counteract some effects of unloading disuse conditions.
authors.affiliation: Laboratory of Neuromuscular Plasticity, University of Sciences and Technologies of Lille, F-59655 Villeneuve d'Ascq, France.
authors.forename: C
authors.initials: C
authors.lastname: Ricart-Firinga
authors.forename: L
authors.initials: L
authors.lastname: Stevens
authors.forename: M H
authors.initials: MH
authors.lastname: Canu
authors.forename: T L
authors.initials: TL
authors.lastname: Nemirovskaya
authors.forename: Y
authors.initials: Y
authors.lastname: Mounier
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001835:Body Weight; D002118:Calcium / Q000494:pharmacology; D002976:Clenbuterol / Q000494:pharmacology*; D019417:Hindlimb Suspension; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000187:drug effects / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D009133:Muscular Atrophy / Q000503:physiopathology; D009929:Organ Size; D051381:Rats; D013324:Strontium / Q000494:pharmacology
chemical_list: D000318:Adrenergic beta-Agonists; D002118:Calcium; D002976:Clenbuterol; D013324:Strontium