Abstract
Food intake, concentration of free amino acids in the brain and plasma and enzyme activity concerning liver amino acid catabolism were examined with young adult rats fed diets containing various levels of protein. Sixteen groups were fed diets containing 3% and from 5 to 75% (in increment of 5%) egg albumin for 10 days. A similar type of experiment with fifteen lebels of dietary casein except for 3% was carried out.
Food intake was depressed in rats fed low protein or high protein diets. A concentration of methionine in the brain was low in the low protein or high protein diets and that of histidine was high in the low protein diets and low in the high protein diets. The activity of serine-threonine dehydratase in the liver increased and concentrations of threonine, serine and glycin in the brain and plasma decreased with increase of protein contents in diets. There was little difference between egg albumin and casein in these profiles of amino acids. Changes in concentrations of methionine and histidine in the brain are suggested to be one of the factors controling food intake.
