Effect of Cortisol on Growth, Food Intake, Dietary Preference and Plasma Amino Acid Pattern of Rats Fed Amino Acid Imbalanced Diets

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Abstract
Since cortisol is known to influence plasma amino acid concentrations and amino acid metabolism in general, rats fed amino acid imbalanced diets have been given cortisol, and growth, food intake, dietary choice and plasma amino acid concentrations have been measured. Food intake and growth of rats fed a threonineor a histidine-imbalanced diet were depressed. However, food intakes of rats injected with cortisol (1 mg/day) and fed the imbalanced diets were not depressed. When rats were offered a choice between the threonine-imbalanced diet and a protein-free diet, they chose the protein-free diet almost immediately, whereas cortisol-injected rats preferred the imbalanced diet. It has been shown that the most limiting amino acid — threonine — in the plasma of rats fed the threonine-imbalanced diet fell below that of the control and the fasting level. Cortisol caused an elevation of the concentration of threonine and of other indispensable amino acids in the plasma of rats fed the imbalanced diet. The increase in the concentration of amino acids in the plasma of cortisol-injected rats, possibly through some redistribution of amino acids within the body, may account for the prevention, by cortisol, of the food intake depression and the change in food preference of rats ingesting the imbalanced diet.