Effect of motor activity on cathepsin D activity in rat muscles.

The effects of acute exhaustive exercise, training and hypokinesia on cathepsin D activity were studied in the superficial ("white") layer of the vastus lateralis, in the deepest ("red") layer of the same muscle, in the soleus, in the heart muscle and in the liver of rats. In was found that acute exercise increased the enzyme activity in both portions of the quadriceps and in the liver. Training increased cathepsin D activity in the "red" quadriceps and in the soleus. In hypokinetic rats cathepsin D activity was markedly increased in each muscle investigated.