Proteolytic enzyme activities and onset of muscular dystrophy in the chick

The relationship between proteolytic enzyme activities, soluble protein profiles, and progression of pathology in dystrophic chick muscle was investigated. Activities of cathepsins C and H, and calcium-activated protease were significantly higher in dystrophic patagialis and pectoralis muscles compared with normal muscles prior to the onset of extensive muscle fiber necrosis. Proteolytic enzyme activity of dystrophic muscle remained constant relative to normal muscle during development while muscle pathology progressed in both patagialis and pectoralis muscles. There were more protein bands (60-80 kDa) in the dystrophic muscle extracts compared with normal at all ages studied. Activities of calcium-activated protease in the dystrophic pectoralis and patagialis were similar although muscle pathology progressed much more rapidly in the dystrophic pectoralis. We conclude there is no causal relationship between the activity of the above proteolytic enzymes and the development of muscle fiber necrosis. The elevated activities of proteolytic enzymes in dystrophic muscle may be due to abnormally accelerated growth.