Effects of the beta-adrenergic agonist cimaterol on chicken muscle atrophy induced by stretch-release.

Thirty-eight White Leghorn chickens, 5 weeks of age, were used to investigate the effect of cimaterol on patagialis muscle (PAT) atrophy due to release of passive-stretch. Cimaterol (CIM) was mixed in a standard commercial chicken diet at 0.5 ppm. Passive-stretch of PAT for 7 days significantly (P < 0.01) increased muscle weight (43%), fiber cross-sectional area (40%) and DNA unit size (34%) compared with unstretched control muscle. In birds fed the standard diet, stretch-release (SR) resulted in immediate and rapid atrophy and by 5 days the stretch-released muscle reached the size of control muscles. In the CIM-fed birds, the atrophy was delayed for 5 days after SR, at which time muscle atrophy at a rate similar to the birds fed the standard diet occurred. It was concluded that cimaterol retarded muscle atrophy induced by stretch-release but the effect was transient and limited to the first 5 days of treatment.