Studies on the alkaline proteinase system in rat skeletal muscle

The alkaline proteolytic activity, as measured with azocasein as substrate, is significantly increased in the musculus extensor digitorum longus 8 days after induction of diabetes mellitus, whereas in soleus muscle, a slightly lower activity is measured when compared to control rats. Ethyleneglycol extraction of the activity from muscles of normal rats and subsequent fractionation by gel filtration revealed three distinct proteinase activities, corresponding to mol. wts. of 120000, 70000 and 18000. Induction of diabetes mellitus in rats is followed by a loss of the 120000 mol.wt. component. Treatment of the diabetic rats with compound 48/80 results in a complete loss of all three proteinase peaks. The activity of a proteinase inhibitor with an apparent mol. wt. of 60000 was unaffected by these manipulations.