The purpose of this study was to gain insight into the production behavior of free adducts of advanced glycation end-products (AGEs) in Wistar rats under acute hyperglycemic conditions. Five AGE-free adducts as well as their precursors ( i.e. , highly reactive carbonyl intermediates of methylglyoxal and glyoxal) in rat plasma were quantitatively determined at greater than nanomolar levels using the liquid chromatography/tandem mass spectrometry method coupled with 2,4,6-trinitrobenzene sulfonate and 2,3-diaminonaphthalene derivatization techniques. An oral glucose (2 g/kg dose) tolerance test to 10-week-old Wistar rats provided evidence that the plasma levels of diabetes-related metabolites did not change acutely within 120 min, irrespective of increasing blood glucose levels.