title: Effects of uremic solutes on reactive oxygen species in vitro model systems as a possibility of support the renal function management.
abstract: BACKGROUND
  In view of the prevalence of oxidative stress in chronic kidney disease (CKD) patients, the loss of low-molecular-weight biomolecules by hemodialysis and the antioxidant potential of some uremic solutes that accumulate in CKD, we used in vitro model systems to test the antioxidant potential of the following uremic solutes: uric acid, hippuric acid, p-cresol, phenol, methylguanidine, L-arginine, L-tyrosine, creatinine and urea.
  
  
  METHODS
  The in vitro antioxidant efficiencies of the uremic solutes, isolated or in mixtures, were tested with the following assays: i) ABTS radical cation decolorization assay; ii) hypochlorous acid (HOCl/OCl(-)) scavenging activity; iii) superoxide anion radical (O2(•-)) scavenging activity; iv) crocin bleaching assay (capture of peroxyl radical, ROO(•)); v) hydrogen peroxide (H2O2) scavenging activity.
  
  
  RESULTS
  Four of the tested uremic solutes (p-cresol, phenol, L-tyrosine, uric acid) were effective antioxidants and their IC50 were found in three model systems: ABTS(•+), HOCl/OCl(-) and crocin bleaching assay. In the 4-solutes mixtures, each one of the solute captured 12.5% for the IC50 of the mixture to ABTS(•+) or HOCl/OCl(-), exhibiting a virtually exact additive effect. In the 2-solutes mixtures, for ROO(•) capture, it was observed the need of more mass of uremic solutes to reach an IC50 value that was higher than the projected IC50, obtained from the IC50 of single solutes (25% of each, in the binary mixtures) in the same assay. In model systems for O2(•-) and H2O2, none of the uremic solutes showed scavenging activity.
  
  
  CONCLUSIONS
  The use of the IC50 as an analytical tool to prepare and analyze mixtures allows the determination of their scavenging capacities and may be useful for the assessment of the antioxidant status of biological samples under conditions of altered levels of the endogenous antioxidant network and/or in the employment and monitoring of exogenous antioxidant therapy.
authors.affiliation: Department of Clinical Analysis, School of Pharmaceutical Sciences, São Paulo State University - UNESP, Rua Expedicionários do Brasil 1621, Araraquara, CEP 14801-902, São Paulo, Brazil. renatapires_17@hotmail.com.
authors.forename: Renata P
authors.initials: RP
authors.lastname: Assis
authors.affiliation: Department of Biochemistry and Technological Chemistry, Institute of Chemistry, São Paulo State University - UNESP, Rua Prof. Francisco Degni 55, Araraquara, CEP 14800-900, São Paulo, Brazil. castrojfa@gmail.com.
authors.forename: Juliana F A
authors.initials: JF
authors.lastname: Castro
authors.affiliation: Department of Clinical Analysis, School of Pharmaceutical Sciences, São Paulo State University - UNESP, Rua Expedicionários do Brasil 1621, Araraquara, CEP 14801-902, São Paulo, Brazil. vania_orteg@hotmail.com.
authors.forename: Vânia O
authors.initials: VO
authors.lastname: Gutierres
authors.affiliation: Department of Clinical Analysis, School of Pharmaceutical Sciences, São Paulo State University - UNESP, Rua Expedicionários do Brasil 1621, Araraquara, CEP 14801-902, São Paulo, Brazil. carlos_arcaro@hotmail.com.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Arcaro
authors.affiliation: Department of Clinical Analysis, School of Pharmaceutical Sciences, São Paulo State University - UNESP, Rua Expedicionários do Brasil 1621, Araraquara, CEP 14801-902, São Paulo, Brazil. squariz@ig.com.br.
authors.forename: Renata S
authors.initials: RS
authors.lastname: Brotto
authors.affiliation: Department of Biochemistry and Technological Chemistry, Institute of Chemistry, São Paulo State University - UNESP, Rua Prof. Francisco Degni 55, Araraquara, CEP 14800-900, São Paulo, Brazil. olgamascarenhaso@gmail.com.
authors.forename: Olga M M F
authors.initials: OM
authors.lastname: Oliveira
authors.affiliation: Department of Clinical Analysis, School of Pharmaceutical Sciences, São Paulo State University - UNESP, Rua Expedicionários do Brasil 1621, Araraquara, CEP 14801-902, São Paulo, Brazil. baviera@fcfar.unesp.br.
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Baviera
authors.affiliation: Department of Clinical Analysis, School of Pharmaceutical Sciences, São Paulo State University - UNESP, Rua Expedicionários do Brasil 1621, Araraquara, CEP 14801-902, São Paulo, Brazil. brunetti@fcfar.unesp.br.
authors.forename: Iguatemy L
authors.initials: IL
authors.lastname: Brunetti
mesh_terms: D001120:Arginine / Q000378:metabolism; D015415:Biomarkers / Q000652:urine; D003404:Creatinine / Q000378:metabolism; D003408:Cresols / Q000378:metabolism; D006626:Hippurates / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007677:Kidney Function Tests; D008760:Methylguanidine / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D006435:Renal Dialysis / Q000009:adverse effects / Q000379:methods*; D051436:Renal Insufficiency, Chronic / Q000628:therapy* / Q000652:urine; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D014443:Tyrosine / Q000378:metabolism; D014508:Urea / Q000378:metabolism; D014527:Uric Acid / Q000378:metabolism
chemical_list: D015415:Biomarkers; D003408:Cresols; D006626:Hippurates; D017382:Reactive Oxygen Species; C032538:4-cresol; D014527:Uric Acid; D014443:Tyrosine; D008760:Methylguanidine; D014508:Urea; D001120:Arginine; D003404:Creatinine; C030514:hippuric acid