title: Gas chromatography-mass spectrometry assay for determination of Ntau-methylhistamine concentration in canine urine specimens and fecal extracts.
abstract: OBJECTIVE
  To develop and validate a gas chromatography-mass spectrometry (GC-MS) method for determination of Ntau-methylhistamine (NMH) concentration in canine urine and fecal extracts and to assess urinary NMH concentrations in dogs with mast cell neoplasia and fecal NMH concentrations in dogs with protein-losing enteropathy.
  
  
  METHODS
  Urine specimens were collected from 6 healthy dogs and 7 dogs with mast cell neoplasia. Fecal extracts were obtained from fecal specimens of 28 dogs with various severities of protein-losing enteropathy, as indicated by fecal concentration of alpha1-proteinase inhibitor.
  
  
  METHODS
  NMH was extracted directly from urine, and fecal specimens were first extracted into 5 volumes of PBSS containing 1% newborn calf serum. Ntau-methylhistamine in specimens was quantified via stable isotope dilution GC-MS. The assay was validated via determination of percentage recovery of known amounts of NMH and interassay coefficients of variation. Urinary excretion of NMH was evaluated by means of NMH-to-creatinine concentration ratios.
  
  
  RESULTS
  Recovery of NMH in urine and fecal extracts averaged 104.6% and 104.5%, respectively. Interassay coefficients of variation ranged from 5.4% to 11.7% in urine and 12.6% to 18.1% in fecal extracts. Urinary NMH excretion was significantly increased in dogs with mast cell neoplasia, compared with that in healthy dogs. No correlation was detected between severity of protein-losing enteropathy and fecal NMH concentration.
  
  
  CONCLUSIONS
  This method provided a sensitive, reproducible means of measuring NMH in canine urine and fecal extracts. High urinary NMH-to-creatinine concentration ratios in dogs with mast cell neoplasia are consistent with increased histamine release in this disease.
authors.affiliation: Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843-4474, USA.
authors.forename: Craig G
authors.initials: CG
authors.lastname: Ruaux
authors.forename: Jeannie M
authors.initials: JM
authors.lastname: Wright
authors.forename: Jörg M
authors.initials: JM
authors.lastname: Steiner
authors.forename: David A
authors.initials: DA
authors.lastname: Williams
mesh_terms: D000818:Animals; D004283:Dog Diseases / Q000378:metabolism*; D004285:Dogs; D005243:Feces / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods / Q000662:veterinary*; D008415:Mastocytosis / Q000378:metabolism / Q000662:veterinary*; D008761:Methylhistamines / Q000032:analysis / Q000652:urine*; D011504:Protein-Losing Enteropathies / Q000378:metabolism / Q000662:veterinary*; D054928:Validation Studies as Topic
chemical_list: D008761:Methylhistamines; C031205:3-methylhistamine