title: Molecular impact of clenbuterol and isometric strength training on rat EDL muscles.
abstract: Clenbuterol, a beta2-adrenergic-receptor agonist, is known to provoke muscle hypertrophy and a slow-to-fast phenotype change. A more glycolytic phenotype should be paralleled by changes in muscle glycolytic metabolism. Two groups (n=16 for each) of 3-month-old male Wistar rats (UCL: untrained clenbuterol, and ECL: exercised clenbuterol) received a chronic administration of clenbuterol (2 mg/kg body weight/day). Two other groups of animals (U: untrained and E: exercised), were given a 0.9% NaCl solution instead of clenbuterol. E and ECL animals followed an 8-week progressive isometric force strength-training program. Both clenbuterol administration and training resulted in an increase in extensor digitorum longus (EDL) mass despite the fact that this muscle was indirectly mobilised during isometric force strength training. Clenbuterol and training induced a consistent slow-to-fast phenotype change without drastically increasing specific activities of glycolytic enzymes. Except for GAPDH and hexokinase, modifications in glycolytic-enzyme-specific activities were not explained by transcriptional changes. Lactate dehydrogenase activity was not affected by clenbuterol but was strongly augmented by training. In EDL of ECL rats, both treatments presented an opposite effect compensating each other. GLUT1 mRNA expression was augmented in EDL of UCL and ECL animals, whereas monocarboxylate transporter 1 mRNA amounts were decreased in EDL of UCL rats. Citrate synthase activity was reduced by clenbuterol treatment but remained unchanged in EDL of E animals. Creatine kinase activity was enhanced only by clenbuterol alone. These data show that clenbuterol-induced muscle hypertrophy and slow-to-fast phenotype changes are not associated with a glycolytic-enzyme-activity increase. They also suggest that in EDL isometric force strength training can reverse clenbuterol-induced molecular adaptations.
authors.affiliation: Faculté de médecine, Laboratoire Inter-Universitaire de Biologie de l'Activité Physique et Sportive, 28 Place Henri Dunant, 63001, Clermont-Ferrand, France. remimounier@voila.fr
authors.forename: Rémi
authors.initials: R
authors.lastname: Mounier
authors.forename: Hélian
authors.initials: H
authors.lastname: Cavalié
authors.forename: Gérard
authors.initials: G
authors.lastname: Lac
authors.forename: Eric
authors.initials: E
authors.lastname: Clottes
mesh_terms: D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002950:Citrate (si)-Synthase / Q000235:genetics / Q000378:metabolism; D002976:Clenbuterol / Q000008:administration & dosage / Q000494:pharmacology*; D003402:Creatine Kinase / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D051272:Glucose Transporter Type 1 / Q000235:genetics; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating) / Q000378:metabolism; D006019:Glycolysis / Q000187:drug effects; D006593:Hexokinase / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007537:Isometric Contraction / Q000187:drug effects*; D008297:Male; D027501:Monocarboxylic Acid Transporters / Q000235:genetics; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D018995:Myosin Heavy Chains / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017526:Receptor, IGF Type 1 / Q000097:blood; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000235:genetics; D000099233:Monocarboxylate Transport Protein 1
chemical_list: D000318:Adrenergic beta-Agonists; D002950:Citrate (si)-Synthase; D002976:Clenbuterol; D003402:Creatine Kinase; D051272:Glucose Transporter Type 1; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating); D006593:Hexokinase; D007334:Insulin-Like Growth Factor I; D027501:Monocarboxylic Acid Transporters; D018995:Myosin Heavy Chains; D020033:Protein Isoforms; D012333:RNA, Messenger; D017526:Receptor, IGF Type 1; D027981:Symporters; D000099233:Monocarboxylate Transport Protein 1; C495679:Slc2a1 protein, rat