1993 Volume 16 Issue 2 Pages 195-198
We tried to measure glycated proteins by a novel method based on colorimetry of 2-keto-glucose which is released from the glycated protein (ketoamine) on heating with hydrazine. Reaction conditions were optimized with glycated human serum albumin (glc HSA) as a model compound. Ketoamine reacted quantitatively with hydrazine on heating at 100°C for 0.5 h, followed by heating with phenylhydrazine at 60°C for 1 h. Glucose interference with the assay was eliminated by preincubation of the sample with glucose oxidase at 37°C for 0.5 h. Time courses for the coloration of glc HSA and human serum showed a profile similar to that of N-p-tolyl-D-isoglucosamine under optimized reaction conditions. The lower limit for the assay of glc HSA was 0.7 μM. The serum level of glycated proteins measured by the present method correlated well with that (fructoamine value, μM) measured by the conventional method (nitroblue tetrazolium-reducing method) (r=0.92, n=35). In conclusion, the present method is a novel, highly sensitive and reliable one for measuring glycated proteins in biological samples.
