Lysine — Arginine Antagonism in the Chick

Abstract

When a casein-gelatin diet supplemented with excess L-lysine was fed to young chicks, it produced symptoms that included abnormalities in bone composition and reduced growth rate. Free amino acids were compared in tissues from chicks receiving the diet with added lysine (2%) and from controls. The most marked effects of the lysine were a reduction in arginine and an increase in lysine in tissues. Supplementary arginine in the diet eliminated the symptoms, increased tissue arginine concentration, and returned growth rate and bone composition to normal. A decrease in cellular K concentration, calculated either from chloride or from sodium space, was related only to dietary supplementation with lysine and not to growth rate. Chicks receiving 2 and 4% lysine added to a soy α-protein ration did not exhibit symptoms; plasma and muscle lysine concentrations increased, and arginine concentration decreased slightly in muscle only. Since these animals and those receiving the casein-gelatin diet supplemented with lysine and arginine had the highest tissue lysine concentrations, lysine per se is not toxic. A difference in amino acid composition of the basal diets does not appear to be the explanation for these observations. It is suggested that excess dietary lysine induces an arginine deficiency by decreasing the availability of arginine from casein or gelatin or from a combination of them.