[Radioimmunoassay of nonenzymatically glucosylated albumin].

A radioimmunoassay (RIA), to quantitate nonenzymatically glucosylated albumin (GA), was established. Antiserum A was obtained by immunizing guinea pigs with reduced glucosylated guinea pig albumin (RedGlc-GPA), and antiserum B was obtained by immunizing with reduced glucosylated human albumin (RedGlc-HA) and absorbing the antibody against human native albumin. For antiserum A; RedGlc-GPA and NaBH4-reduced guinea pig serum, in which epsilon-N-1-(1-deoxy glucitol) lysine (GL) was present, were effective competitors. But NaBH4-reduced human serum, NaBH4-reduced human hemoglobin, and RedGlc-HA, in which GL were also present, were not so effective competitors. For antiserum B; RedGlc-HA, and RedGlc-GPA, in which GL were present, and GL were equally effective competitors. Thus it seemed that for antiserum A, the antigenic region was not only GL, and for antiserum B, the antigenic region was GL almost specifically. So we used antiserum B for this RIA, and GA in NaBH4-reduced human albumin was quantitated by measuring its ability to compete for antibody binding, compared with that of GL as a standard. Reproducibility of GA-values with this RIA was a enough to use for clinical purpose. With this RIA method, the following results were obtained: 1) These GA values were correlated with GA values, measured by boronate-affinity chromatographic method. 2) Average of GA values in 44 diabetics was significantly higher than that of 24 normal subjects. 3) These GA values were also correlated with HbA1, HbA1c, and fasting blood sugar (FBS). 4) These GA values were more closely correlated with FBS, 2 weeks before, than with FBS, at the same time, and with FBS, 4 weeks before. 5) After insulin treatment to untreated diabetics, these GA values were more rapidly decreased than HbA1c. These result indicated that GA values quantitated in this RIA was available for monitoring blood sugar level for shorter period than that represented by HbA1c.