The identification of 4, 6-quinolinediol and 4,8-quinolinediol in the urine of hens

No evidence for a physiological role of 5-hydroxykynuramine in chicken hemostasis

Pharmacological effects of 5-hydroxykynuramine (5-HK) were investigated in chicken whole blood. It was shown that 5-HK had a time-depending inhibiting activity on platelet aggregation induced by 5-hydroxytryptamine (5-HT). Experiments were carried out in order to determine whether the inhibitory effect of chicken aorta upon 5-HT-induced aggregation of chicken whole blood could be explained by the formation of 5-HK, a metabolite of 5-HT. Using high performance liquid chromatography (HPLC) in combination with sensitive electrochemical detection, the presence of 5-HK could not be confirmed in chicken blood or aortic tissue, despite the fact that 5-HT levels of chicken blood (6.78 +/- 0.54 micrograms/ml) and aorta (0.69 +/- 0.11 micrograms/g of tissue wet weight) could be determined. These results do not point to a physiological role of 5-HK in chicken whole blood aggregation.

Evidence for presence of kynurenine in lung and brain of neonate hamsters

Using immunocytochemical techniques, we report here direct evidence of kynurenine (Kyn) presence and localization in the lung and brain. Kyn is a metabolite of tryptophan and 5-hydroxytryptophan, produced by indoleamine 2,3-dioxygenase (IDO). Whereas IDO has been quantitated in tissues from lung, brain, and other organs, Kyn has only been identified in brain (by HPLC), and its specific localization has not been determined. We reacted alternate serial paraffin sections with antisera raised in rabbits against a L-Kyn-albumin conjugate, and with anti-5HT (serotonin, 5-hydroxytryptamine), using the PAP method. Kyn-like immunoreactivity in the lung was specifically localized to cells of the bronchiolar epithelium resembling basal cells. Taller epithelial cells in the bronchi and dorsal trachea were likewise positive whereas neuroepithelial bodies were negative. Immunoreactivity in the brain was typically localized to cells localized in the ependyma of the walls of all ventricles, and to nerve fibers. The cellular Kyn-like reactivity was totally separate from that of anti-5HT, the latter uniquely staining argyrophil lung neuroendocrine cells and raphae neurons of the brain. Our findings suggest a route of tryptophan metabolism in the lung and brain alternate to the common pathway leading to 5-hydroxyindoleacetic acid via 5-HT. This route is of physiologic and pathologic significance as many metabolites are pharmacologically active.

Antagonism of 5-hydroxykynurenamine against serotonin action on platelet aggregation

Serotonin induced an aggregation of human platelets, whereas 5-hydroxykynurenamine, produced from serotonin by the action of indoleamine 2,3-dioxygenase, did not cause any significant degree of platelet aggregation. 5-Hydroxykynurenamine specifically inhibited both a serotonin-induced aggregation of platelets and the potentiation of the ADP-induced platelet aggregation by serotonin. It did not, however, alter the profiles of the platelet aggregation induced by ADP, collagen, or adrenaline. The degree of inhibition was proportional to the time of preincubation of platelets with 5-hydroxykynurenamine, and to the concentration of 5-hydroxykynurenamine used. Available evidence indicated that 5-hydroxykynurenamine completed with serotonin for the same receptor sites. Studies with analogues of 5-hydroxykynurenamine indicated that the substitutions of 0-amino-benzyl moiety with hydroxy or methoxy groups were somewhat tolerated, whereas the masking of alkylamine moiety with N-acetylation completely lost the inhibitory activity.

Tryptophan 5-hydroxylase in rat intestine

Tryptophan 5-hydroxylase was partially purified from rat small intestine and characterized. The enzyme activity was mainly localized in the distal one-fourth of the small intestine. The enzyme required Fe(2+), 2-amino-4-hydroxy-6,7-dimethyl-5,6,7,8-tetrahydropteridine and oxygen for full activity. The pH optimum of the reaction was 8.0. The hydroxylation rate of d-tryptophan by the enzyme was one-third that of l-tryptophan. l-Phenylalanine and l-tyrosine could not serve as substrates. The physiological significance of the enzyme is discussed.

Isolation for 6-hydroxykynurenic acid from the tobacco leaf

1. 6-Hydroxykynurenic acid (4,6-dihydroxyquinoline-2-carboxylic acid, 6-HKA) was isolated in crystalline form from both green and cured tobacco leaves. 2. A method for the determination of 6-HKA by paper chromatography and fluorimetry is described. 3. The content of 6-HKA in the flowers, stem and roots of the tobacco plant was much lower than that in the leaf. 4. The 6-HKA content increased throughout leaf development and senescence. 5. 6-HKA was detected in the leaves of plants representing 11 out of 27 families sampled. 6. 6-HKA was found to be devoid of antibacterial and antifungal activity, and was inactive in the Avena-coleoptile and cress-seed-germination tests. 7. The presence of 6-HKA is taken as evidence in plants of the tryptophan-catabolic pathway already known in mammals and micro-organisms.