The chicken dystrophic model: Does hypersensitivity to glucocorticoids cause atrophy?

The characteristics of the glucocorticoid receptor population in skeletal muscle and liver from line 412 (normal) and line 413 (dystrophic) chickens were examined. The results demonstrate that in cytosol of pectoralis major muscle from line 412 animals there is a precipitous decrease in the number of receptor sites that occurs between 7 and 14 days ex ovo, followed by a slow decline in the number of sites as the animal matures. The results obtained from the examination of pectoralis major muscle from line 413 are considerably different. Although there is a decrease in the number of sites in the cytosol of pectoralis major muscle from line 413 animals it is delayed by at least 2 weeks. In addition, the number of sites in these muscles is still at least twice that observed in the muscle from normal line 413 animals. Even at 60 days ex ovo the number of receptors in pectoralis major muscle from line 413 animals is more than twice that observed in the comparable muscle from line 412 animals. In addition, the gastrocnemius muscle from older animals (90 days ex ovo) was examined. By comparing this red-fiber muscle from line 412 and line 413 animals, we found a significantly higher number of sites in the gastrocnemius muscle from dystrophic animals. No difference was observed in the glucocorticoid receptor population in the livers of normal and dystrophic animals.