Decreased lysosomal protease content of skeletal muscles from streptozotocin-induced diabetic rats: a biochemical and histochemical study.

The activity of four lysosomal proteases in soleus and extensor digitorum longus muscles was studied in streptozotocin-induced diabetic rats using newly developed fluorescence histochemical and biochemical techniques. The results indicate that the content of lysosomal protease in skeletal muscle cells was decreased three weeks after the induction of diabetes. The reduction was most pronounced in the extensor digitorum longus for all the proteases tested, but in the soleus only cathepsin B and dipeptidyl peptidase II showed a decrease. Biochemical assays on total muscle homogenates and muscle extracts confirmed the histochemical observations that protease activity was significantly lower in diabetic muscles. This decrease in activity varied with the duration of diabetes beginning as early as 48 h for the soleus. In conclusion, myofibre-specific decreases in lysosomal proteases occur following diabetes.