Clenbuterol, a beta 2-adrenergic agonist, reverses muscle wasting due to scald injury in the rat.

The effects of clenbuterol, a beta 2-adrenergic agonist, on body weight, tissue masses, and protein and RNA contents were studied following scald injury (30 per cent TBSA) in the rat. While the masses of heart, liver and epididymal fat pads remained unaffected, significant reductions in gastrocnemius, plantaris and soleus muscle masses (approximately 11 per cent; P < 0.01) were observed following injury, none of which were mimicked by pair-feeding or could be attributed to dehydration. This muscle wasting was accompanied by significant reductions in protein and/or RNA content. Oral administration of clenbuterol (4 mg/kg diet) had no anabolic effects, either in the scalded animals or their pair-fed controls. While clenbuterol (12 mg/kg diet) did not affect the masses of heart and fat pads, increases in the wet weights (approximately 20 per cent), RNA (approximately 30 per cent) and protein content (approximately 20 per cent) of the gastrocnemius and plantaris muscles were observed in all animals; the magnitude of these effects was greater (P < 0.05) in the scalded animals than in their pair-fed controls. Clenbuterol had no effect on body weight but increased (P < 0.001) carcass water content. These data indicate that there is a selective mobilization of muscle protein and sparing of fat in the early phase following burn injury, and that beta 2-adrenergic agonists, such as clenbuterol, may be of therapeutic value in inhibiting or reversing muscle atrophy associated with thermal injury.