Protein carbamylation, a nonenzymatic posttranslational modification promoted during
uremia, is linked to a poor prognosis. In the present study, carbamylation of
serum albumin was assayed using the symmetry factor on a capillary electrophoresis instrument (Helena V8). The symmetry factor has been defined as the distance from the center line of the peak to the back slope, divided by the distance from the center line of the peak to the front slope, with all measurements made
at 10% of the maximum peak height.
Serum albumin,
creatinine, and
urea concentrations were assayed using routine methods, whereas
uremic toxins were determined using HPLC. In vitro carbamylation induced a marked
albumin peak asymmetry. Reference values for the
albumin symmetry factor were 0.69-0.92. In kidney patients,
albumin peak asymmetry corresponded to the
chronic kidney disease stage (p < 0.0001). The symmetry factor correlated well with serum
urea (r = -0.5595, p < 0.0001) and
creatinine (r = -0.5986, p < 0.0001) concentrations. Several
protein-bound
uremic toxins showed a significant negative correlation with the symmetry factor. Morphology of the
albumin fraction was not affected by presence of glycated
albumin and
protein-bound
antibiotics. In conclusion, the presented method provides a simple, practical way for monitoring protein carbamylation.