title: Liver protein synthesis. Molecular weight distribution of pulse-labeled polypeptide chains in normal and thyroidectomized rats.
abstract: Equations are presented for determination of elongation rate in vivo for a heterogenous population of polypeptide chain molecular weights. The distribution of pulse-labeled polypeptide chains in rat liver deoxycholate-soluble protein has been obtained by sodium dodecyl sulfate-gel electrophoresis and used to compute a theoretical curve for determination of synthesis time of a 50000 mol. wt. polypeptide chain (tc50). Values of tc50 for normal and thyro-parathyroidectomized Long-Evans male rats were 1.2 and 1.75 min, respectively, representing protein synthetic rates of about 7.5 and 5.1 mg protein/g liver/h. No difference in the molecular weight profile of liver polypeptide chains on the basis of labeling or Amido-black staining was observed between the two groups. The distributions of radioactivity before and after secretion of labeled plasma protein are compared. The role of protein-synthetic rate in the changing enzyme levels associated with thyroid hormone is discussed.
mesh_terms: D000818:Animals; D005260:Female; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008970:Molecular Weight; D010452:Peptide Biosynthesis; D010441:Peptide Chain Elongation, Translational; D051381:Rats; D013965:Thyroidectomy; D013997:Time Factors