title: Correlation between the plasma tryptophan to neutral amino acid ratio and protein intake in the self-selecting weanling rat.
abstract: The relationship between changes in blood plasma amino acids and the quantity of protein and energy self-selected by the weanling rat, simultaneously offered two diets varying only in protein concentration, was examined. The changes in the quantity of protein and energy consumed by the rats, which were brought about by the addition of the essential limiting amino acids and groups of essential amino acids to gluten, casein, and zein, were not linearly related to alterations in the total plasma amino acid concentrations or to the accumulation of the added amino acids in the blood plasma. However a consistent relationship between food intake and plasma acids was identified when the plasma tryptophan to neutral amino acid ratio was correlated with the protein intake selected. It is postulated that the ratio of tryptophan to neutral amino acids in the plasma is involved in, or reflects, a mechanism regulating protein intake.
mesh_terms: D000596:Amino Acids / Q000097:blood*; D000818:Animals; D002364:Caseins / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage / Q000592:standards; D004734:Energy Metabolism; D005518:Food Preferences; D005527:Food, Fortified; D005983:Glutens / Q000008:administration & dosage; D008239:Lysine / Q000008:administration & dosage; D008297:Male; D051381:Rats; D014364:Tryptophan / Q000097:blood*; D015028:Zein / Q000008:administration & dosage
chemical_list: D000596:Amino Acids; D002364:Caseins; D004044:Dietary Proteins; D005983:Glutens; D014364:Tryptophan; D015028:Zein; D008239:Lysine