title: Comparison of the nutritive values of L-, DL- and D-tryptophan in the rat and chick.
abstract: Experiments were designed to compare the nutritive values of L-, DL- and D-tryptophan in rats and chicks. Growing rats and chicks were fed for 19 and 21 days, respectively, diets containing amino acid mixtures with graded levels of either L-, DL- or D-tryptophan so that the regression of weight gain or protein retention on tryptophan intake could be established. After the end of the experiments, plasma free L-tryptophan was estimated by a microbiological method. The nutritive values of DL- and D-tryptophan relative to the L-isomer were 47 and 21%, respectively in chicks and close to 100% in rats. In chicks, plasma free L-tryptophan concentration increased with the increase of L- and DL-tryptophan levels in the diet, but remained at a low level regardless of the D-tryptophan level in the diet. In rats, however, a good correlation was observed between plasma free L-tryptophan and tryptophan level in the diet.
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002645:Chickens / Q000378:metabolism*; D008297:Male; D009753:Nutritive Value; D011506:Proteins / Q000378:metabolism; D051381:Rats / Q000378:metabolism*; D013045:Species Specificity; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014364:Tryptophan / Q000097:blood / Q000378:metabolism*
chemical_list: D011506:Proteins; D014364:Tryptophan