Protein synthesis in skeletal muscle from normal and diabetic rats following increased contractile activity in situ.

Protein synthesis was measured in rat skeletal muscle after one hour of heavy work. Direct, supramaximal electrical stimulation in situ under anesthesia resulted in an increase in the in vitro rate of protein synthesis in the soleus and gastrocnemius muscles during the next two hours. Most of the increase was located in the nuclear-connective tissue fraction. No increase was observed in the actomyosin, microsomal or soluble fractions. The same pattern was also observed in the flacid contralateral soleus. Passive stretch of the same muscle group did not result in such changes in protein synthesis. The response was obliterated by rendering the rat diabetic. The observed increase in protein synthesis may represent the initial stages of the adaptive response to increases in muscular activity.