title: A novel, quantitative assay for homocarnosine in cerebrospinal fluid using stable-isotope dilution liquid chromatography-tandem mass spectrometry.
abstract: We describe a rapid and sensitive method for the quantification of homocarnosine in physiological fluids, with particular emphasis on cerebrospinal fluid (CSF). Homocarnosine was quantified as the butyl derivative, with (2)H(2)-l-homocarnosine as internal standard. Following deproteinization of CSF samples, supernatants were evaporated to dryness and derivatized with 10% 6M HCl in butanol. Samples were chromatographed on a C(18) column and detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS) operating in the multiple reaction monitoring mode. The intra- and inter-assay variations were 4.6 and 10.9%, respectively. Mean recovery of homocarnosine at two concentrations was 105%. The limit of detection in CSF approximated 20 nmol/L. CSF homocarnosine is age dependent and ranges from <0.02 to 10 micromol/L. Our method is applicable to the analysis of CSF derived from patients with heritable defects in the GABA pathway, patients with homocarnosinosis or serum carnosinase deficiency, and should be applicable to other model systems in order to further explore the biological role and significance of homocarnosine in mammalian systems.
authors.affiliation: Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Erwin E W
authors.initials: EE
authors.lastname: Jansen
authors.forename: K Michael
authors.initials: KM
authors.lastname: Gibson
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Shigematsu
authors.forename: Cornelis
authors.initials: C
authors.lastname: Jakobs
authors.forename: Nanda M
authors.initials: NM
authors.lastname: Verhoeven
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002336:Carnosine / Q000031:analogs & derivatives* / Q000134:cerebrospinal fluid; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003903:Deuterium; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D013058:Mass Spectrometry / Q000379:methods*; D008875:Middle Aged; D011865:Radioisotope Dilution Technique; D012015:Reference Standards; D012016:Reference Values; D015203:Reproducibility of Results; D005680:gamma-Aminobutyric Acid / Q000134:cerebrospinal fluid
chemical_list: C005038:homocarnosine; D005680:gamma-Aminobutyric Acid; D002336:Carnosine; D003903:Deuterium