Muscle atrophy in rats following denervation, casting, inflammation, and tenotomy.

One week after unilateral denervation, tenotomy, casting, or joint inflammation, skeletal muscles of adult female Wistar rats were studied to determine the effect of these processes on muscle weights and fiber diameters of the soleus, the red and white regions of the plantaris, plus muscle weights and protein content of the gastrocnemius. All atrophic processes caused greater weight loss of the soleus than of the plantaris or gastrocnemiums. Within the soleus and plantaris muscles, the type-I fiber atrophy was equal to the type-II fiber atrophy except for the white region of the plantaris following tenotomy, where the wasting of the type-I fiber was greater than that of type II. This study also demonstrated that denervation, tenotomy, casting, and inflammation resulted in a greater loss of myofibrillar proteins (content and absolute amounts) than of sarcoplasmic and stromal proteins. Denervation generally was found to have the greatest effect on the parameters evaluated. The findings are consistent with the hypothesis that slow muscle is more dependent than fast muscle on neuronal control, and that nerve controls muscle through the dual role of impulse activity and axoplasmic flow.