Anabolic effects of clenbuterol on skeletal muscle are mediated by beta 2-adrenoceptor activation

Abstract

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.

β2 adrenergic agonist, clenbuterol, enhances working memory performance in aging animals

“…It is also used to treat mild-to-moderate stress incontinence (Noguchi et al, 1997) and allergic inflammation (Yoshimura et al, 1997). However, clenbuterol is also abused by individuals that practice body building because of β2 agonists' anabolic effects and reduction of subcutaneous fat (Choo et al, 1992;Hesketh et al, 1992;Navegantes et al, 2001;Prather et al, 1995;Ryall et al, 2004;Yimlamai et al, 2005). Thus, clenbuterol would seem like an attractive option for preventing muscle frailty in the elderly as has been suggested from a study in rats (Ryall et al, 2004).…”

Acute clenbuterol overdose resulting in supraventricular tachycardia and atrial fibrillation

“…Its longer duration of action yields a prolonged high serum level as compared to other β 2 -agonists: this makes clenbuterol a desired agent for body-building [4,5]. Clenbuterol increases the rate of muscle protein deposition leading to enlargement of individual muscle fibers [2,5,6].…”

“…Clenbuterol increases the rate of muscle protein deposition leading to enlargement of individual muscle fibers [2,5,6]. In addition, clenbuterol promotes lipolysis in humans and animals through adipocyte β 3 -adrenoreceptors, encouraging the body to burn fatty acids [4][5][6]. Therefore, weight gain is a result of muscle hypertrophy and not fat accumulation.…”

“…Clenbuterol hydrochloride, a β 2 -adrenoreceptor agonist used for the treatment of asthma and chronic obstructive pulmonary disease (COPD), is quickly gaining popularity because of its anabolic effects and ability to promote lipolysis [1][2][3][4][5][6]. However, misuse from inexperienced users have resulted in severe adverse reactions [1,[7][8][9][10][11].…”

Metabolic responses of the whole body, portal-drained viscera and hindquarter to adrenaline infusion: Effects of nonselective and selective β-adrenoceptor blockade

“…Additionally, epinephrine infusion caused a reduction of most plasma amino acids in normal and diabetic humans (Shamoon et al 1980) which was reversed by propranolol, thus suggesting an effect of the β-adrenoceptor system in protein and amino acid metabolism. β-adrenoceptor processes mediate protein accretion in animals (Choo et al 1992). Simulation by β-adrenergic agonists results in increased thermogenesis and protein accretion in ruminants (MacRae et al 1988).…”