The effects of intraperitoneal clenbuterol injection on protein degradation and myostatin expression differ between the sartorius and pectoral muscles of neonatal chicks

Gen Comp Endocrinol. 2014 Sep 15;206:111-7. doi: 10.1016/j.ygcen.2014.07.023. Epub 2014 Aug 10.


The purpose of this study was to investigate the effects of injection of the β2-adrenergic receptor agonist clenbuterol on the skeletal muscles of neonatal chicks (Gallus gallus domesticus). One-day-old chicks were randomly divided into four groups and given a single intraperitoneal injection of clenbuterol (0.01, 0.1, or 1mg/kg) or phosphate-buffered saline. Twenty-four hours after the injection, the sartorius muscles (which consist of both slow- and fast-twitch fibers) of chicks that received 0.01 or 0.1mg/kg clenbuterol were significantly heavier than those of controls, while there were no between-group differences in the weight of the pectoral muscles, which consist of only fast-twitch fibers. Muscle free N(t)-methylhistidine, regarded as an index of myofibrillar proteolysis, was decreased in the sartorius muscle of the clenbuterol-injected chicks, while it was not affected in the pectoral muscles. In the sartorius muscle of the clenbuterol-injected chicks, myostatin and atrogin-1/MAFbx mRNA expressions were decreased, while insulin-like growth factor-I was unaffected. These observations suggested, in 1-day-old chicks, clenbuterol might increase mass of the sartorius muscle by decreasing myostatin gene expression and protein degradation.

Keywords: Gallus gallus domesticus; Muscle growth; Myofibrillar proteolysis; β(2)-Adrenergic receptor.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Agonists / administration & dosage*
  • Adrenergic beta-Agonists / pharmacology
  • Animals
  • Animals, Newborn
  • Chickens / metabolism*
  • Clenbuterol / administration & dosage*
  • Clenbuterol / pharmacology
  • Gene Expression Regulation / drug effects*
  • Injections, Intraperitoneal
  • Insulin-Like Growth Factor I / genetics
  • Insulin-Like Growth Factor I / metabolism
  • Male
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism*
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / metabolism*
  • Myostatin / genetics
  • Myostatin / metabolism*
  • Pectoralis Muscles / cytology
  • Pectoralis Muscles / drug effects
  • Pectoralis Muscles / metabolism
  • Proteolysis / drug effects*
  • RNA, Messenger / genetics
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction


  • Adrenergic beta-Agonists
  • Muscle Proteins
  • Myostatin
  • RNA, Messenger
  • Insulin-Like Growth Factor I
  • Clenbuterol