General Stimulation of Muscle Protein Synthesis by Branched Chain Amino Acids in Vitro 1

Abstract

Summary

The effect of branched chain amino acids on precursor incorporation into soluble and myofibrillar protein fractions of muscle was examined with a double-label technique, polyacrylamide gel electrophoresis and isoelectric focusing. Rat hemidiaphragms were incubated in medium containing [¹⁴C]-tyrosine or [³H]tyrosine with or without 0.5 mM leucine, isoleucine and valine. Branched chain amino acids stimulated synthesis of soluble and myofibrillar protein fractions equally, approximately 60%, p < .001. They promoted tyrosine incorporation into individual proteins of both fractions without preferential stimulation of the synthesis of particular proteins. The lack of selectivity of the stimulatory effect is compatible with an effect on translation.