Myosin in developing normal and dystrophic chicken pectoralis. II. The relationship between intracellular and extracellular aspartate pools and myosin synthesis.

The present studies establish the cellular pool of aspartate as the major source of this amino acid used during the biosynthesis of skeletal muscle myosin. The precursor=product relationship has been established in growing, normal pectoralis and has been suggested in hypertrophied, dystrophic pectoralis. Specific activities of aspartic acid in plasma and cellular pools corrected for extracellular space contributions have been correlated with aspartate incorporation onto myosin. These data have been coupled with quantitative data on myosin accumulation and have established the cellular pool as the major precursor pool. The data also give further insight into some of the factors responsible for the observation that in vivo dystrophic tissue gives higher levels of aspartate incorporation than normal tissue.