title: Plasma cysteine/cystine reduction potential correlates with plasma creatinine levels in chronic kidney disease.
abstract: OBJECTIVE
  Oxidative stress has been considered a nontraditional risk factor for cardiovascular disease in the chronic kidney disease (CKD) population, possibly triggered by uremic toxicity.
  
  
  METHODS
  A chromatographic method with coulometric detection was adapted to directly and simultaneously determine cysteine (Cys) and cystine (Cyss) in plasma samples. Healthy subjects and CKD subjects in different stages were analyzed. The free Cys and free Cyss levels in their plasma were determined, and the reduction potential [Eh(Cyss/2Cys)] was calculated with the Nernst equation.
  
  
  RESULTS
  Healthy plasma presented Eh(Cyss/2Cys) of -123 ± 7 mV. Plasma Eh(Cyss/2Cys) correlated significantly with creatinine levels (p < 0.0001, r = 0.62).
  
  
  CONCLUSIONS
  Plasma Eh(Cyss/2Cys) correlated with increased levels of plasma creatinine, supporting the view that uremia triggers oxidative stress. In addition, it may be used as a quantitative oxidative stress biomarker in uremic conditions.
authors.affiliation: Departamento de Patologia Básica, Universidade Federal do Paraná, Centro Politécnico, Curitiba, Brazil.
authors.forename: Silvia D
authors.initials: SD
authors.lastname: Rodrigues
authors.forename: Giuseppe B
authors.initials: GB
authors.lastname: Batista
authors.forename: Max
authors.initials: M
authors.lastname: Ingberman
authors.forename: Roberto
authors.initials: R
authors.lastname: Pecoits-Filho
authors.forename: Lia S
authors.initials: LS
authors.lastname: Nakao
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D003404:Creatinine / Q000097:blood*; D003545:Cysteine / Q000097:blood*; D003553:Cystine / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress; D051436:Renal Insufficiency, Chronic / Q000097:blood*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D003553:Cystine; D003404:Creatinine; D003545:Cysteine