Evidence for a selective stimulation of myosin synthesis following muscle denervation

The incorporation of radioactive leucine into newt triceps muscle was measured at intervals up to 24 hr following denervation of the muscle. Incorporation, measured either by total acid-precipitable radioactivity or summation of activity in fractions obtained by disc gel electrophoresis of muscle proteins, was initially stimulated by up to 70% for a period of up to 12 hr after denervation. Subsequently, the incorporation fell below that found in control muscles. When muscle proteins were fractionated by electrophoresis to determine which protein species were labeled, it was found that between 2 and 10 hr after denervation there was marked stimulation of incorporation into a protein of molecular weight approximately 200,000 to 235,000 that corresponds to a subunit of myosin. After 10 hr the pattern of leucine incorporation into the protein species was the same for both normal and denervated muscles. One neural mechanism, removed by denervation, may be responsible for both restriction of myosin synthesis and maintenance of overall protein synthesis, but we suggest that more than one factor is involved.