The response of the rat soleus muscle to tenotomy after dorsal root section

Calcium-activated protease activity in tenotomized muscle

The purpose of this study was to investigate the possible role of calcium-activated neutral protease in the disorganization and dissolution of the myofibrils of the rat soleus that occurs following tenotomy. Rats were killed 3, 5, 7, 14, 21, and 42 days after tenotomy of the soleus, and the muscles were removed and assayed for calcium-activated protease activity. Maximal protease activity occurred 1 week after tenotomy, at the time when myofibril organization is completely disrupted. Activity was still high 2 and 3 weeks after the operation, but returned to normal levels by 6 weeks, when muscle histology had returned to normal. The time course of the calcium-activated protease activity corresponded closely to the time course of the morphological changes. Thus, calcium-activated neutral protease may play a major role in myofibrillar proteolysis following tenotomy and in making the myofibril susceptible to proteolytic attack by other, less specific proteases.

Modifications in the histochemical and biochemical changes in tenotomized rat soleus by denervation

Response of tenotomized rat soleus muscle to denervation performed at different time intervals, has been investigated. Tenotomized muscles showed typical central core lesions seven days post-operatively. These were not observed in m-ATPase stained sections of simultaneously denervated and tenotomized muscles, and muscles denervated 24 h after tenotomy. Central core lesions were not prevented in muscles denervated 28 h after tenotomy, indicating that tenotomy effects responsible for central lesions are completed by this time. Myosin light chain pattern of muscles denervated 28 h after tenotomy, and tenotomized only were similar showing increased LC3/LC1 ratio. Simultaneously denervated and tenotomized muscle however showed all the three light chains relatively equal in quantity. The results suggest that elimination of neural activation within 28 h prevents myofibrillar loss and minimized other changes which occur due to tenotomy.

The development of central cores in both fiber types in tenotomized muscle

Using the histochemical reaction for myosin adenosine triphosphatase (ATPase), a study of the rat soleus muscle following tenotomy was undertaken. It was demonstrated that both type 2A and 2C fibers undergo degenerative changes following tenotomy. All previous studies have stated that only type 1 fibers were affected and developed central core lesions and that type 2 fibers were somehow protected from the degenerative process. The results of this experiment illustrate that central core lesions will develop in all three fiber types (types 1, 2A, and 2C) of the soleus following tenotomy.