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Photosensitized Oxidation of Tryptophan: Effect on Liver and Brain Tryptophan
Author(s) -
Bhatia Jatinder,
Rassin David K.,
Mcadoo David J.
Publication year - 1991
Publication title -
journal of parenteral and enteral nutrition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.935
H-Index - 98
eISSN - 1941-2444
pISSN - 0148-6071
DOI - 10.1177/0148607191015006637
Subject(s) - tryptophan , riboflavin , chemistry , serotonin , biochemistry , fluorescence , ultraviolet light , chromatography , amino acid , photochemistry , physics , receptor , quantum mechanics
Toxic products are formed when tryptophan is irradiated with light in the presence of photosensitizers such as riboflavin. In order to further investigate this phenomenon, solutions of tryptophan (48 μmol·mL −1 ) were irradiated with broad spectrum fluorescent light in the presence or absence of riboflavin (0.01 mg.mL −1 ). Solutions of riboflavin were similarly irradiated; control solutions were the respective solutions not exposed to light. Two‐week‐old suckling gerbils were then assigned to receiving 7 days of intraperitoneal injections of the light‐exposed or non‐light‐exposed solutions. There were significant differences in the concentrations of tryptophan in serum, liver, and brain; activity of gamma‐glutamyl transferase (GGT) as well as liver protein were also significantly different among the groups. Body and liver weights were also significantly different among the groups. In order to identify the photoproducts responsible for these changes, solutions of tryptophan that had been irradiated with light in the presence of riboflavin were then fractionated based on time of elution during high‐pressure liquid chromatography and the fractions were then injected into the gerbils as before. GGT responses to one of the fractions was similar to that of the parent compound. Chromatographic studies indicated the presence of numerous photoadduct compounds of tryptophan and riboflavin after exposure to light. Both the presence of riboflavin and the exposure of the solutions to light alter brain concentrations of tryptophan in the developing gerbil indicating differing availability to the brain of this serotonin precursor. Clinical implications of the infusion of amino acids in the presence of photosensitizers and light must be considered. ( Journal of Parenteral and Enteral Nutrition 15:637–641, 1991)