Interrelationships between Dietary Methionine and Cystine as Reflected by Growth, Certain Hepatic Enzymes and Liver Composition of Weanling Rats

Abstract

To investigate quantitative relationships between methionine and cystine, experimental diets fed to weanling rats contained 4.8, 3.6, and 2.4 mmoles of sulfur amino acids and at each level methionine furnished 100, 75, 50 and 25% of the total and cystine 0, 25, 50 and 75%, respectively. Both the level of total sulfur-containing amino acids and the relative proportion of methionine and cystine significantly influenced food intake, weight gain, nitrogen deposition and specific activity of cystathionase in hepatic tissue but only the relative proportions of methionine and cystine altered specific activity of cystathionine synthase in liver. Interaction between level of total sulfur-containing amino acids and proportion of methionine and cystine was significant in respect to all parameters tested.