Effects of denervation on calpain and calpastatin in hamster skeletal muscles.

Three leg muscles (soleus, extensor digitorum longus, and plantaris) of adult male golden Syrian hamsters were denervated by bilateral transecting of the sciatic nerve. Eighteen days after denervation, wet weights, amounts of soluble protein, and activities of wide-specificity calpain II, intermediate filament protein-specific calpain I, and calpastatin were measured by protein determination and enzyme and immunological assays. In comparison with control (nondenervated) muscles and depending on the specific muscle and protein, the activities of the calpains increased 1.3 to 1.9 times the control values, whereas the calpastatin decreased to one-half and one-third of control values. The muscle which showed the greatest increase in both calpain activities and the largest decrease in calpastatin activity was the plantaris (a fast-twitch, oxidative glycolytic muscle). The extensor digitorum longus (fast-twitch glycolytic) showed increases in calpain II activity similar to those in the plantaris, but smaller changes in calpain I and calpastatin. The soleus (slow-twitch, oxidative) showed the smallest changes in calpain II and calpastatin activities, although an increase in the calpain I activity was seen after denervation. These results suggest a possible relationship between the presence of fast-twitch, oxidative glycolytic fibers in a muscle and increased potential for intracellular proteolysis following denervation.