Application of the time-resolved immunofluorometric assay to the study of C3 complement component glycation in vitro and in vivo.

A time-resolved immunofluorometric assay (TR-IFMA) was used for the measurement of glycated C3. The very high sensitivity of this technique allowed the direct measurement of glycated and non-glycated proteins (especially C3) in chromatography eluates. C3 glycation in vitro after incubation with 20 mmol/l glucose was always less than 3.5% by day 5. As determined with the TR-IFMA, the means +/- standard deviations of glycated C3 were 0.20% +/- 0.04 for non-diabetic subjects and 0.88% +/- 0.06 for insulin-dependent diabetic patients. The low percentages of glycated C3 in both our in vitro and in vivo studies show that this protein is subject to only moderate rates of glycation.