Metabolism of an oral tryptophan load. I: Effects of dose and pretreatment with tryptophan

British Journal of Clinical Pharmacology
A R GreenH F Woods

Abstract

1 The metabolism of three oral doses of L-tryptophan (50, 25 and 10 mg/kg) in healthy young males has been investigated. 2 There was a linear relationship between both peak and area under curve of the total plasma tryptophan concentrations whilst the relationship between these parameters and plasma free tryptophan was hyperbolic. 3 Before the tryptophan load about 85% of plasma tryptophan was bound to albumin. As plasma tryptophan concentrations increased there was a hyperbolic increase in free tryptophan. Scatchard analysis revealed 1.4 binding sites/molecule albumin with a dissociation constant (Kd) of 57.9 microM. Following administration of L-tryptophan (50 mg/kg) twice daily for 7 days there was no alteration in the number of binding sites but the dissociation constant (Kd) had decreased to 30.9 microM. 4 L-Tryptophan (50 mg/kg twice daily for 7 days) markedly increased both basal plasma total and free tryptophan. However following a further load the total tryptophan curve was comparable to that seen after acute administration. The plasma free tryptophan curve was lowered relative to that seen after an acute dose. 5 Increasing the tryptophan dose shortened the plasma half-life and decreased the volume of distribution and t...Continue Reading

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Citations

Jan 1, 1994·Journal of Neural Transmission. General Section·C J Clayton, R E Hicks
May 26, 2012·The European Journal of Neuroscience·Eiko Nakamaru-OgisoKatsuji Takai
Dec 1, 1980·British Journal of Clinical Pharmacology·A R Green, J K Aronson
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Jun 29, 2010·Journal of Affective Disorders·Nadia IovienoDavid Mischoulon
Oct 25, 2016·Trends in Pharmacological Sciences·Jacob P R JacobsenMarc G Caron
Feb 10, 2017·Journal of Forensic Sciences·Niha Ansari, Shobhana K Menon
Aug 2, 2013·Journal of Psychopharmacology·Abdulla A-B Badawy
Mar 9, 2018·Harvard Review of Psychiatry·Brent M KiousPerry F Renshaw
Mar 23, 2009·International Journal of Tryptophan Research : IJTR·Dawn M RichardDonald M Dougherty
Feb 28, 2020·International Journal of Molecular Sciences·Joosep PaatsAlberto Arduan Ortiz
Sep 7, 2019·International Journal of Tryptophan Research : IJTR·Abdulla A-B Badawy, Gilles Guillemin
Oct 1, 1985·British Journal of Clinical Pharmacology·A R GreenP J Cowen
Nov 11, 2019·Experimental Gerontology·Abdulla A-B Badawy

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