Uptake and Release of Tryptophan and Serotonin: An HPLC Method to Study the Flux of Endogenous 5-Hydroxyindoles Through Synaptosomes |
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Authors: | William A Wolf Donald M Kuhn |
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Institution: | Section on Biochemical Pharmacology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, U.S.A. |
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Abstract: | An HPLC assay with fluorometric detection has been developed that is sensitive enough to measure simultaneously endogenous levels of tryptophan, serotonin (5-hydroxytryptamine, or 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) inside synaptosomes as well as that released into the incubation medium. Using this assay, we have observed that tryptophan is rapidly taken up by synaptosomes and turned over to 5-HIAA without a concurrent release of 5-HT. Exogenous 5-HT is also rapidly taken up, and, within 20-30 min, 80% of the 5-HT is deaminated. Veratridine induces release of both tryptophan and 5-HT from synaptosomes. Changes in the disposition of exogenous tryptophan or 5-HT can be completely accounted for by uptake or by stoichiometric changes in metabolites. This assay method should be valuable in the study of 5-HT pools and in the determination of from which pool 5-HT release occurs. |
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Keywords: | Serotonin 5-Hydroxytryptamine Synaptosomes HPLC Release Uptake Monoamine oxidase |
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