Turnover of Structural Protein Fractions in Denervated Muscle.

Abstract

Studies were made of the incorporation of a radioactive amino acid into various fractions of rat skeletal muscle structural proteins in vivo and in vitro, in order to compare protein turnover in different fractions within a muscle and to characterize the differences in protein turnover between similar fractions from denervated atrophying and control muscles. The in vivo studies indicated that fractions of structural protein extracted by different solvents had different patterns of incorporation and loss of label. No precursor-product relationships were found among the 3 extracted fractions of myosin. The in vivo study also revealed, in general, an uptake of label into fractions from atrophying muscle equal to or greater than that of the comparable control muscle fractions, followed by decreasing levels of activity in the fractions from atrophying muscle while activity remained higher in similar fractions from control muscle. Studies with muscle slices showed a markedly greater rate in synthesis of structural proteins during atrophy.