title: Sodium octanoate to reverse indoxyl sulfate and p-cresyl sulfate albumin binding in uremic and normal serum during sample preparation followed by fluorescence liquid chromatography.
abstract: Indoxyl sulfate and p-cresyl sulfate are protein-bound marker molecules in chronic kidney disease. Recent findings suggest that indoxyl sulfate and p-cresyl sulfate directly contribute to the uremic syndrome. A method for quantification of p-cresyl sulfate and indoxyl sulfate total serum concentrations was developed. We used sodium octanoate as competitor to replace non-covalent binding of p-cresyl sulfate and indoxyl sulfate to albumin. Total, within-run, between-run and between-day imprecision for indoxyl sulfate and p-cresyl sulfate were all below 6%. The limit of quantification was 3.2microM for both analytes. Recovery, tested in hemodialysis patients, was 102% for indoxyl sulfate and 105% for p-cresyl sulfate. Deming regression demonstrated good agreement for indoxyl sulfate between this new method and an external HPLC method. Method comparison for p-cresyl sulfate of the new method with our in-house GC-MS method demonstrated good agreement, whereas method comparison with an external HPLC method revealed a small proportional bias. Sodium octanoate binding competition is a novel sample preparation that allows for direct quantification of indoxyl sulfate and p-cresyl sulfate.
authors.affiliation: Department of Medicine, University Hospital Gasthuisberg, Leuven, Belgium.
authors.forename: Henriette
authors.initials: H
authors.lastname: de Loor
authors.forename: Björn K I
authors.initials: BK
authors.lastname: Meijers
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Meyer
authors.forename: Bert
authors.initials: B
authors.lastname: Bammens
authors.forename: Kristin
authors.initials: K
authors.lastname: Verbeke
authors.forename: Wim
authors.initials: W
authors.lastname: Dehaen
authors.forename: Pieter
authors.initials: P
authors.lastname: Evenepoel
mesh_terms: D000418:Albumins / Q000378:metabolism*; D002210:Caprylates / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods*; D003408:Cresols / Q000097:blood*; D005453:Fluorescence; D006801:Humans; D007200:Indican / Q000097:blood* / Q000652:urine*; D007674:Kidney Diseases / Q000097:blood / Q000652:urine; D011485:Protein Binding; D012680:Sensitivity and Specificity; D013463:Sulfuric Acid Esters / Q000097:blood*
chemical_list: D000418:Albumins; D002210:Caprylates; D003408:Cresols; D013463:Sulfuric Acid Esters; C408690:4-cresol sulfate; D007200:Indican; C031492:octanoic acid