Effects of Loading with Tryptophan Metabolites on Metabolism of DL-Tryptophan-7a-C11 in Rats.

SummaryDL-tryptophan-7a-C14 was administered intraperitoneally to adult rats at a level of 0.715 mg/kg of body weight. In some experiments loads of L-tryptophan, kynu-renine, hydroxyanthranilic acid or quinolinic acid (equivalent on a molar basis to 2 g of L-tryptophan in a 70 kg man) were given 30 minutes prior to the labeled tryptophan. Rats given a tracer dose of DL-tryptophan-7a-C14 excreted 18-20% of the C14 as C14O2 and 7.2-7.6% in the urine in the first 12 hours. The injection of a load of L-tryptophan 30 minutes prior to the DL-tryptophan- 7a-C14 caused an increase in C14O2 to 33.6% of the dose and the urinary C14 level increased to 9.1%. The injection of 0.14 mM/kg of 3-hydroxyanthra-nilic acid 30 minutes prior to administration of the labeled tryptophan caused a depression of the C14O2 excretion to 8.8% and increased the urinary C14 level to 23.6%. Autoradio-graphs of chromatograms of the urines and C14 analyses of more than 8 of the known tryptophan metabolites isolated from the urines showed t...