Cathepsins A, B, C, D and autolysis during development of breast muscle of normal and dystrophic chickens

Abstract

Cathepsins A, B, C, and D have been shown to be present in lysosome-like particles in breast muscle of 1-week-old control chickens. The activities of these enzymes, as well as the extent of autolysis at acid pH, and noncollagen protein content have been investigated during development of breast muscle of the normal chicken and the chicken with hereditary muscular dystrophy from 13–14 days in ovo to 3–4 months after hatching. The same parameters were also investigated in soleus muscle of the 3- to 4-month control chicken. In dystrophic as compared to control breast muscle, the following observations were made: significantly higher levels of cathepsin A activity were found at 1 week ex ovo; cathepsin B activity and autolysis were sigficantly increased at 2 weeks ex ovo at which stage of development a significant decrease in protein content was also first apparent; Cathepsins C and D activities were not significantly elevated until 1 month after hatching. Proteolytic activity of the soleus muscle (red) was found to be substantially greater and the protein content lower than that of normal breast muscle (white) and in these respects qualitatively resembled dystrophic breast muscle. These results are discussed in the light of a mechanism for the initiation of the muscle-wasting process in the chicken with hereditary muscular dystrophy.