Enhanced whole-body protein synthesis by methionine and arginine supplementation in protein-starved chicks

Abstract

1. The effect of supplementing with methionine alone or in combination with arginine on whole-body protein synthesis and degradation was studied in protein-starved chicks, fed on a protein-free (PF) diet, by a massive-dose injection of L-[4- 3 H]phenylalanine. 2. Methionine or methionine and arginine (MA) supplementation reduced body-weight loss and improved N balance compared with unsupplemented controls.3. Whole-body protein synthesis was significantly increased both in terms of fractional rate and absolute amounts by methionine and MA addition, whereas the fractional degradation rate was unchanged.4. No significant difference was found between methionine and MA supplementation except for energy balance of the birds.5. It was concluded that the N-sparing effect of methionine or MA when added to a PF diet was primarily brought about by enhanced whole-body protein synthesis.