Abstract
To develop a systematic method for the measurement of glucose turnover using stable isotope labeled glucose, fragmentation pathway of differential species of glucose labeled with 13C or 2H was analyzed by gas chromatography/mass spectrometry (GC/MS). Among the various methods for derivatizing glucose, trifluoroacetylation of glucose was demonstrated to be most suitable for the systemic tracer dilution study because of reasonable stability of isotopic peak ratios and strong ion peaks of high mass area. Under euglycemic hyperinsulinemic clamp conditions with four different insulin infusion rates, glucose turnovers were determined using [6, 6-2H2]-glucose as a tracer in normal conscious male Sprague-Dawley rats. The mean hepatic glucose production rate during the basal state was 7.2mg/kg. min. The maximal glucose uptake response of the peripheral tissues to insulin during the clamp was 42.1mg/kg. min and the arterial plasma insulin level at EC50 was 45μ/ml. HGP was almost completely suppressed at a plasma insulin level of 100μU/ml. These findings are corsistent with those of previous reports using radioisotopes as traceris. Thus, the stable isotope technique in which trifluoroacetylated glucose is analyzed on GC/MS may serve as a useful method for studying glucose metabolism in vivo.
