Anabolic effects of clenbuterol on skeletal muscle are mediated by beta 2-adrenoceptor activation.
The potent anabolic effects of the beta 2-adrenoceptor agonist clenbuterol on skeletal muscle have been reported to be independent of actions on beta-adrenoceptors. In the present study clenbuterol, presented to rats in the diet (4 mg/kg), caused significant increases in gastrocnemius muscle mass, protein, and RNA content and a decrease in epididymal fat pad mass. These effects were not mimicked by oral administration of the beta 2-adrenoceptor agonist salbutamol even at high dose (52 mg/kg diet), and the effects of clenbuterol were not inhibited by addition of DL-propranolol (200 mg/kg diet). However, the selective beta 2-antagonist ICI-118,551 (200 mg/kg diet) reversed the anabolic effects of clenbuterol, and a high dose of DL-propranolol (1,000 mg/kg diet) also inhibited these actions of clenbuterol. Furthermore, continuous infusion of salbutamol (1.15 mg.kg body wt-1.day-1) via miniosmotic pumps did cause significant increases in muscle mass, protein, and RNA content. These results indicate that the anabolic effects of clenbuterol are dependent on interaction with the beta 2-adrenoceptor. However, a long duration of action appears to be required to induce the anabolic effects of beta 2-agonists.
Choo
J J
JJ
Department of Physiological Sciences, University of Manchester Medical School, United Kingdom.
Horan
M A
MA
Little
R A
RA
Rothwell
N J
NJ
D000420:Albuterol / Q000494:pharmacology; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002976:Clenbuterol / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D000420:Albuterol; D002976:Clenbuterol