Determination of Glycated Proteins in Biological Samples Based on Colorimetry of 2-Keto-glucose Released with Hydrazine

Abstract

We developed a novel method for measuring glycated (glc) proteins in biological samples, based on the colorimetry of 2-keto-glucose which is released from the glc protein (ketoamine) on heating with hydrazine. The ketoamine-induced coloration remained constant at room temperature (25—27 °C) for 1 h. The method gave reliable precision and accuracy. However, high concentrations of serum pigments caused positive interference, suggesting that hemolytic or hyperbilirubinemic serum would give false-positive results. The concentration of glc protein in clinical serum samples measured by the present method (y) correlated well with those (fructosamine values, x) measured by the nitroblue tetrazolium-reducing method: y=1.27x-1.69 (r=0.92, n=93). The concentrations (μm, mean±S.D.) of glc protein in sera from normal and diabetic subjects were 275 ±37 (n=32) and 403 ±98 (n=32), respectively, and the concentrations (nmol/mg hair, mean±S.D.) of glc protein in back hairs from non-diabetic and diabetic rats were 3.7 ±0.3 (n=10) and 8.6 ±1.5 (n = 10), respectively. Thus, the technique gave reasonable concentrations of glc proteins in humans and rats with diabetes mellitus, indicating it to be reliable and diagnostically useful. © 1994, The Pharmaceutical Society of Japan. All rights reserved.