Effect of clenbuterol on growth and body composition during food restriction in rats

The effect of long-term exposure to combinations of growth promoters in Long Evans rats

The aim of the study was to investigate whether the chronic administration (45 days) of clenbuterol (CB) at a growth promoting dose (1 mg kg(-1) bw) and/or dexamethasone (DEX: 0.1 mg kg(-1) bw) may cause the disruption of rat endocrine adrenal function. Blood samples were taken weekly during the whole experiment (S0-S7), and at different days of withdrawal (W0, W5, W10, W15 and W20). Hormone profiles were determined by RIA (ACTH) or EIA (corticosterone and catecholamines). ACTH showed significantly elevated concentrations from S1 until W5 (p<0.05) with CB administration. It began to decrease the day of DEX and CB-DEX administration. DEX showed significantly lowered ACTH concentrations from the day of drug injection (p<0.05). Corticosterone showed significantly elevated levels until W10 (p<0.01) with CB and CB+DEX. DEX showed lowered levels of corticosterone during the whole withdrawal period. Epinephrine presented significantly elevated plasma levels until W5 with CB and CB+DEX. With DEX, epinephrine was also elevated from W5 to W15 (p<0.05). Norepinephrine also presented significantly elevated plasma levels until S7 with CB and CB+DEX (p<0.001). With DEX no differences were found.

CONCLUSION

Long-term administration of CB and/or DEX causes an endocrine adrenal disruption with changes in ACTH, glucocorticoid and catecholamine secretion.

Beta-agonist-induced alterations in organ weights and protein content: comparison of racemic clenbuterol and its enantiomers

Clenbuterol is a relatively selective beta2-adrenergic partial agonist that has bronchodilator activity. This drug has been investigated as a potential countermeasure to microgravity- or disuse-induced skeletal muscle atrophy because of presumed anabolic effects. The purpose of this study was to: 1) analyze the anabolic effect of clenbuterol's (-)-R and (+)-S enantiomers (0.2 mg/kg) on muscles (cardiac and skeletal) and other organs; and 2) compare responses of enantiomers to the racemate (0.4 mg/kg and 1.0 mg/kg). Male Sprague Dawley rats were treated with: a) racemic clenbuterol (rac-clenbuterol, 0.4 or 1.0 mg/kg); b) enantiomers [clenbuterol (-)-R or (+)-S]; or c) vehicle (1.0 mL/kg buffered saline). Anabolic activity was determined by measuring tissue mass and protein content. HPLC teicoplanin chiral stationary phase was used to directly resolve racemic clenbuterol to its individual enantiomers. In skeletal muscle, both enantiomers had equal anabolic activity, and the effects were muscle- and anatomic region-specific in magnitude. Although the enantiomers did not affect the ventricular mass to body weight ratio, clenbuterol (+)-S induced a small but significant increase in ventricular mass. Both clenbuterol enantiomers produced significant increases in skeletal muscle mass, while being less active in producing cardiac ventricular muscle hypertrophy than the racemic mixture.

A, Martínez R. J, Martínez de A. A. Effect of clenbuterol on growth performance in broilers

The objective of this study was to evaluate the effect of clenbuterol (CB), a beta2-adrenergic agonist, as a growth and weight gain promoter in broilers. Effects of CB were assessed, mixing it in feed at 0.0, 0.21, 0.42 and 0.84ppm, and feeding during four weeks to four groups (n=75) of 28 day-old Arbor Acres chickens. The body weight (BW) and food intake at 0, 12, 20 and 28 days of the study were recorded. Also abdominal fat (AF) and total muscle proteins were measured. Results indicate that from day 20 until the last of the experimental period (56-day-old), efficacy of CB was evident to increase growth and decrease AF deposition rates (P<0.01), in a dose-response pattern, suggesting that CB has a profitable growth promoting effect in broiler chickens.