320 AJVR, Vol 70, No. 3, March 2009 T he assessment of gastrointestinal mucosal permea- bility and absorptive capacity provides information about gastrointestinal mucosal function. Nonmetabo- lizable markers, such as polyethylene glycol, sugars, or radiolabeled substances, have been widely used. 1 Al- tered intestinal permeability has been reported in hu- mans with inflammatory bowel disease and also in other animals with experimentally induced gastroin- testinal tract disease. 2 In humans and dogs, intestinal permeability generally increases with the severity of disease. 3,4 Intestinal permeability has been postulated to be responsible for the introduction of antigenic or infectious agents through the intestinal mucosa, which can lead to excessive immunogenic stimulation. 5,6 Currently, monosaccharides and disaccharides are widely used to assess abnormalities of gastrointestinal permeability and mucosal absorptive capacity. 7 Except Development and analytic validation of a gas chromatography–mass spectrometry method for the measurement of sugar probes in canine serum Heriberto Rodriguez, MVZ, MS; Jan S. Suchodolski, Dr med vet, PhD; Nora Berghoff, Dr med vet; Jörg M. Steiner, Dr med vet, PhD Objective—To develop and analytically validate a gas chromatography–mass spectrometry (GC-MS) method for the quantification of lactulose, rhamnose, xylose, 3-O-methylglucose, and sucrose in canine serum. Sample Population—Pooled serum samples from 200 dogs. Procedures—Serum samples spiked with various sugars were analyzed by use of GC-MS. The method was analytically validated by determination of dilutional parallelism, spiking recovery, intra-assay variability, and interassay variability. Results—Standard curves ranging from 0.5 to 500 mg/L for each sugar revealed a mean r 2 of 0.997. The lower detection limit was 0.03 mg/L for lactulose, rhamnose, xylose, and methylglucose and 0.12 mg/L for sucrose. The observed-to-expected ratios for dilutional parallelism had a mean ± SD of 105.6 ± 25.4% at dilutions of 1:2, 1:4, and 1:8. Analytic re- coveries for the GC-MS assays of sugars ranged from 92.1% to 124.7% (mean ± SD, 106.2 ± 13.0%). Intra-assay coefficients of variation ranged from 6.8% to 12.9% for lactulose, 7.1% to 12.8% for rhamnose, 7.2% to 11.2% for xylose, 8.9% to 11.5% for methylglucose, and 8.9% to 12.0% for sucrose. Interassay coefficients of variation ranged from 7.0% to 11.5% for lactulose, 6.4% to 9.4% for rhamnose, 6.8% to 13.2% for xylose, 7.0% to 15.9% for methylglucose, and 5.5% to 9.4% for sucrose. Conclusions and Clinical Relevance—The GC-MS method described here was accurate, precise, and reproducible for the simultaneous measurement of sugar probes in canine serum. (Am J Vet Res 2009;70:320–329) for mannitol, which is believed to be synthesized in only small quantities in humans 8 but is not believed to be syn- thesized in other animals, 9 both groups of sugar probes (ie, monosaccharides and disaccharides) are not con- sidered to be endogenously synthesized in mammalian species. 8 Therefore, serum concentrations of these sug- ars are considered to exclusively originate from gastro- intestinal permeability and absorption. Use of a mixture of monosaccharide and disaccha- ride probes is based on the assumption that the intesti- nal epithelium is a heteroporous layer. 10 Aqueous pores are distributed along the crypt-villus axis of the small intestinal mucosa. Small channels (radius < 0.6 nm) are relatively abundant at the tips of the villi, which allows Received February 7, 2008. Accepted May 28, 2008. From the Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843-4474. Presented in part at the 25th Annual Forum of the American College of Veterinary Internal Medicine, Seattle, June 2007. Address correspondence to Dr. Steiner. ABBREVIATIONS CV Coefficient of variation GC-MS Gas chromatography–mass spectrometry HPLC High-performance liquid chromatography m/z Mass-to-charge ratio O/E Observed-to-expected PAD Pulsed amperometric detection SIM Selective ion monitoring TMS Trimethylsilyl Unauthenticated | Downloaded 08/20/22 12:15 PM UTC