Radioimmunoassay of glycated serum protein using monoclonal antibody to glucitollysine and coomassie-brilliant-blue-coated polystyrene beads.

A radioimmunoassay for glycated serum protein (GSP) was developed using monoclonal antibody to glucitollysine and polystyrene beads coated with Coomassie-Brilliant-Blue (CBB) as adsorbent for serum protein. The monoclonal antibody was raised by immunizing BALB/c mice with reduced glycated LDL and fusing their spleen cells with mouse myeloma cells. CBB-coated polystyrene beads were introduced to absorb a constant amount of serum protein. The protein adsorbed on the CBB-coated beads was reduced by NaHB4, and after treatment with radiolabeled antibody, the radioactivity of each bead was counted with an automatic gamma-counter. The standard glycated protein used was reduced glycated human serum albumin, in which 8 of 59 lysine residues were glycated. The intra- and interassay coefficients of variation of GSP were 4.8-6.5% and 1.6-6.0%, respectively. The GSP level of diabetic patients was significantly higher than that of normal controls (1.97 +/- 1.23 vs. 0.47 +/- 0.21 nmol/mg-protein; mean +/- SD, p less than 0.001). The GSP levels of patients with insulin-dependent and non-insulin-dependent diabetes mellitus were 3.03 +/- 1.05 and 1.51 +/- 1.00 nmol/mg-protein, respectively. A good correlation was found between the levels of GSP and hemoglobin A1c (HbA1c) (r = 0.85, p less than 0.001). In patients admitted to the hospital for diabetes education and glycemic control, the GSP level decreased 43 +/- 12% with the decrease in the fasting plasma glucose level (39 +/- 13%) and the mean daily plasma glucose level (MPG, 47 +/- 15%) in a four week period after admission, whereas the HbA1c level decreased only 13 +/- 6% during this period.(ABSTRACT TRUNCATED AT 250 WORDS)