An Effect of Insulin on Peptide Synthesis independent of Glucose or Amino-Acid Transport

Abstract

INSULIN enhances incorporation of amino-acids labelled with carbon-14 into protein of isolated rat diaphragms independent of its action in facilitating entry of glucose^1–3. Kipnis and Noall⁴ report that in similar circumstances insulin increases the accumulation of ¹⁴C-α-aminoisobutyric acid, a non-utilizable amino-acid. If the rate of penetration of the utilizable labelled amino-acids is also increased by insulin, the result would be a rise in the radioactivity of the intracellular amino-acid pool. Then an apparent increase in the rate of incorporation could occur without an actual change in the rate of peptide synthesis. This possibility has now been tested. Increased transport does not account for the insulin-mediated increase in the incorporation of utilizable amino-acids.