[Effects of continuous body stress and methandienone on the degradation of myofibrillar proteins in the guinea pig heart and soleus muscle].

The influence of permanent physical stress (running training) and of the application of an anabole-androgenic steroid, 17-beta-hydroxy-17-methylandrosta-1,4-dien-3-on (metandienone, Dianabol) on the degradation rate of myofibrillar proteins of heart and soleus of male guinea-pigs was investigated. The rate of protein degradation was measured by the time-dependent loss of radioactive proteins after labelling with 14C-leucine in vivo. The investigations led to the following results: We found no significant change of the body or muscle weights of any of the guinea-pig groups examined. Only the combination of physical stress with metandienone showed a significant increase of the myofibrillar protein concentration as well as an increase of the specific activity of the myofibrillar proteins of heart and soleus. These findings could be the result of a decreased degradation rate of the myofibrillar proteins. The myofibrillar proteins of the heart were higher labelled than the myofibrillar proteins of the soleus. The concentration of myofibrillar proteins was higher in the soleus than in the heart. The 14C-leucine activity of the free amino acid pool was significantly higher in the heart than in the soleus in the first minutes after labelling.