title: Development of enzyme immunoassay for endogenous ouabain-like compound in human plasma.
abstract: Widespread evidence supports the existence of an endogenous digitalis-like compound in mammals. We report here the development of a novel enzyme immunoassay for ouabain that, in conjunction with a detailed HPLC study, identifies a ouabain-like compound (OLC) in extracted human plasma. The assay is sensitive-minimum detection limit for OLC 37 pmol/L (11 pmol/L in plasma)-and has a working range (between-assay CV < 10%) of 180-10000 pmol/L (54-3000 pmol/L in plasma). Mean recoveries of ouabain added to plasma ranged from 90% to 100%, and plasma extracts diluted in parallel to the standard curve. Plasma OLC concentrations in 10 healthy volunteers averaged 92 pmol/L (range 55-168), assuming 100% cross-reactivity of OLC in the ouabain assay. HPLC analysis with two distinct chromatographic conditions demonstrated that endogenous human plasma OLC co-eluted with authentic ouabain. The enzyme immunoassay is rapid and easy to perform and will support further investigation of the nature of this controversial endogenous steroid.
authors.affiliation: Department of Clinical Biochemistry, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Harwood
authors.forename: J A
authors.initials: JA
authors.lastname: Little
authors.forename: G
authors.initials: G
authors.lastname: Gallacher
authors.forename: D
authors.initials: D
authors.lastname: Perrett
authors.forename: R
authors.initials: R
authors.lastname: Edwards
authors.forename: A
authors.initials: A
authors.lastname: Dawnay
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007124:Immunoenzyme Techniques / Q000706:statistics & numerical data; D008832:Microchemistry; D010042:Ouabain / Q000097:blood*; D011786:Quality Control; D012016:Reference Values; D012680:Sensitivity and Specificity
chemical_list: D010042:Ouabain