The effect of insulin on incorporation of amino acids into protein of normal rat diaphragm in vitro

Abstract

The effect of addition of insulin, glucose and pyruvate on incorporation in vitro into protein of normal rat diaphragm of C14 from C14 amino acids and of S35 from a (S35) amino acid has been studied. Incorporation of radioactivity from the (C14) amino acids glycine, leucine, isoleucine, phenylalanine, serine, lysine, arginine, glutamic acid and aspartic acid, each studied separately, and from a mixture of (C14) amino acids, was increased by addition of insulin both in the presence and absence of glucose or pyruvate. Neither glucose nor pyruvate greatly affected incorporation in the presence or absence of insulin. Incorporation of S35 from (S35) methionine sulfoxide was accelerated by addition of insulin both in the presence and absence of glucose or pyruvate. Addition of glucose slightly increased incorporation in the absence of insulin, but neither glucose nor pyruvate affected incorporation in the presence of insulin. Incorporation of C14 from alanine was increased in the presence of insulin in the absence of glucose or pyruvate, but was markedly decreased in the absence of insulin, by addition of pyruvate or, to a less extent, of glucose; in the presence of these substrates insulin did not stimulate incorporation. The possibility is discussed that this behavior of added alanine is attributable to the formation in muscle of alanine from pyruvate or glucose by a process of transamination.