Decrease in plasma tryptophan after tryptophan-free amino acid mixtures in man.
Male healthy subjects, fasting 12 hours, ingested increasing amounts of a mixture containing a fixed proportion of seven essential amino acids (L-isoleucine 11.5%, L-leucine 18.0%, L-lysine 13.1%, L-methionine 18.0%, L-phenylalanine 18.0%, L-threonine 8.2%, L-valine 13.1%) and lacking tryptophan. The diets produced a rapid fall in plasma tryptophan which was proportional to the total amount of the amino acids ingested. Following the highest dose administered (36.6 g) plasma tryptophan fell to a minimum of about 35% the initial level and remained markedly reduced at 6 hours after treatment. The mechanism of this decrease and its potential clinical relevance are discussed.
Moja
E A
EA
Chair of Psychobiology, Medical School, University of Modena, Italy.
Stoff
D M
DM
Gessa
G L
GL
Castoldi
D
D
Assereto
R
R
Tofanetti
O
O
D000328:Adult; D000601:Amino Acids, Essential / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008297:Male; D008875:Middle Aged; D011897:Random Allocation; D014364:Tryptophan / Q000008:administration & dosage / Q000097:blood*
D000601:Amino Acids, Essential; D004044:Dietary Proteins; D014364:Tryptophan