title: A simple LC-MS/MS method for determination of kynurenine and tryptophan concentrations in human plasma from HIV-infected patients.
abstract: BACKGROUND
  Indoleamine 2,3-dioxygenase, catalyzing tryptophan (Trp) metabolism through the kynurenine (Kyn) metabolic pathway, plays important roles in immune suppression and the CNS. In this article, we report a simple, rapid and specific LC-MS/MS method for accurate determination of Kyn and Trp concentrations in human plasma from HIV-infected patients.
  
  
  RESULTS
  The human plasma sample (100 µl) was mixed with Kyn-d4 and Trp-d5 internal standards and then precipitated with trifluoroacetic acid. The supernatant was directly analyzed by LC-MS/MS. The assay using surrogate matrix calibrators was validated for precision, accuracy, matrix effect, extraction efficiency and stability. Some assay validation issues for endogenous substance bioanalysis using an LC-MS/MS method are discussed.
  
  
  CONCLUSIONS
  A simple, specific and reproducible LC-MS/MS method has been developed and validated for measuring Kyn and Trp in human plasma samples.
authors.affiliation: Drug Studies Unit, Department of Bioengineering & Therapeutic Sciences, University of California, San Francisco, CA 94143, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Huang
authors.forename: Alexander
authors.initials: A
authors.lastname: Louie
authors.forename: Qiyun
authors.initials: Q
authors.lastname: Yang
authors.forename: Nicholas
authors.initials: N
authors.lastname: Massenkoff
authors.forename: Connie
authors.initials: C
authors.lastname: Xu
authors.forename: Peter W
authors.initials: PW
authors.lastname: Hunt
authors.forename: Winnie
authors.initials: W
authors.lastname: Gee
mesh_terms: D002853:Chromatography, Liquid / Q000191:economics / Q000379:methods*; D006678:HIV / Q000302:isolation & purification*; D015658:HIV Infections / Q000097:blood*; D006801:Humans; D007737:Kynurenine / Q000097:blood*; D057230:Limit of Detection; D053719:Tandem Mass Spectrometry / Q000191:economics / Q000379:methods*; D014364:Tryptophan / Q000097:blood*
chemical_list: D007737:Kynurenine; D014364:Tryptophan