Effect of methionine and lysine deficiencies on protein synthesis in the liver and oviduct and in the whole body of laying hens.

For laying hens, protein synthesis in the liver, in the oviduct (magnum and remaining portions), and in the whole body was measured in vivo in order to investigate the effect of a dietary deficiency of methionine or lysine. The rate of protein synthesis in tissues was calculated from the incorporation of L-[15N]phenylalanine into the protein fraction; whole-body protein synthesis was estimated from the plateau enrichment of free [15N]phenylalanine in plasma. The enrichment of labeled phenylalanine was analyzed by using a gas-chromatograph mass spectrometer, following a primed infusion of the isotope for 6 h. The whole-body protein synthesis of laying hens fed diets deficient in amino acids was significantly lower than that of control hens. Protein synthesis in the liver, magnum, and remainder of the oviduct was decreased by a dietary deficiency of the amino acids studied with larger rates of decrease than for the whole-body analysis. The proportion of reduction in protein synthesis resulting from the sum of the tissues studied, compared with that of the whole body, was 36 and 50%, respectively, for a deficiency of methionine and lysine.