Protein Metabolism in Isolated Rat Diaphragm Muscle: Effects of Insulin and Tryptophan

Abstract

Incubation of isolated rat diaphragm in the presence of tryptophan decreased the stimulatory effect of insulin on proline transport. This inhibition of the insulin effect by tryptophan was not via competition for carrier sites since tryptophan itself had no effect on the transport of proline. Tryptophan itself stimulated the incorporation of preaccumulated phenylalanine and the incorporation of label from isotopically labeled sodium pyruvate into diaphragm protein, although the magnitude of the tryptophan effect was not as great as that of insulin. Incubation of the tissues with both tryptophan and insulin resulted in a significant inhibition of the insulin effect on protein synthesis. The results are discussed relative to the possible role of the amino acid in the insulin receptor site in muscle.

Key words

Isolated Rat Diaphragm - Proline Transport - Insulin Effect - Tryptophan Effect