QUANTITATIVE MEASUREMENT OF 3-O-METHYL-D-GLUCOSE BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY AS A MEASURE OF GLUCOSE-TRANSPORT IN-VIVO

Existing methods of measuring glucose kinetics are subject to errors. There is considerable interest in improved methods of measuring glucos e kinetics to allow the development of new regimes for the treatment o f diabetes mellitus. 3-O-Methyl-D-glucose is transported but not metab olized and therefore allows independent estimation of transport parame ters. We describe a method by which 3-O-methyl-D-glucose in plasma sam ples can be measured in protocols during which glucose Bur is assessed with simultaneous use of two isotopically labelled glucoses to quanti tate and validate measurements of the rate of glucose appearance and d isappearance. Quantitative gas chromatographic/mass spectrometric (GC/ MS) analysis of 3-O-methyl-D-glucose, D-glucose, D-[U-C-13]glucose and D-[6,6-H-2(2)]glucose in human plasma using methoxime-trimethylsilyl ether derivatives is described. Measurements of all four derivatives w ere performed together in a small sample volume (50 mu l) with high pr ecision. The intraassay (inter-assay) coefficients of variation at an isotope content of 0.25 atom% excess for D-[6,6-H-2(2)]glucose, D-[U-C -13]glucose and 3-O-methyl-D-glucose were 0.8% (1.0%), 0.5% (4.0%) and 0.1% (3.7%), respectively. This method provides the basis for quantit ative estimation of parameters of glucose kinetics in man and the rate s of glucose flux across the cell membrane.