title: Effects of denervation on the composition and synthesis of sarcolemmal proteins.
abstract: In vitro synthesis of proteins and changes in polypeptide composition of sarcolemma were studied in innervated and denervated extensor digitorum longus muscle of the rat. A technique of evacuating myoplasm from muscle slices was used as a preliminary step in the preparation of three membrane fractions, M, H and S, containing sarcolemma. On the basis of findings from the previous study and the present investigation, it was concluded that the M fraction was most enriched with extrajunctional sarcolemma. In vitro incorporation of [3H]leucine into membrane proteins of the M fraction showed an apparent linear increase in the rate of protein synthesis from 1-10 days after denervation. The relative increase at 10 days was 137% greater than that of innervated controls. Fractions H and S showed a smaller relative increase. Polypeptide composition of M, H and S fractions based on SDS gel electrophoresis of innervated and denervated muscle, showed qualitative and quantitative changes. The most striking difference was a nominal 29 000 component in M that constituted a disproportionately large peak. Following 10 days of denervation the M fraction underwent significant compositional changes in its electrophoretic profile, the most dramatic of which was a large reduction in the proportion of the 19 000 component. The denervation-induced compositional change is discussed in light of known alterations in the chloride conductance of the muscle plasmalemma.
mesh_terms: D000818:Animals; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis*; D008970:Molecular Weight; D009121:Muscle Denervation; D009132:Muscles / Q000378:metabolism*; D010452:Peptide Biosynthesis; D051381:Rats; D012508:Sarcolemma / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins