A radioimmunoassay for an advanced glycosylation endproduct

A competitive radioimmunoassay for an advanced glycosylation endproduct, 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI) was developed. The immunogen was prepared by coupling of 4-furanyl-2-furoyl-1H-imidazole-1-hexanoic acid to keyhole limpet hemocyanin. The antiserum obtained by immunizing guinea pigs with the immunogen exhibited high affinity binding to FFI, but no cross-reactivity was observed for structurally related compounds containing an imidazole ring or furan ring(s). By using the radioimmunoassay, the levels of FFI in bovine serum albumin incubated with glucose for varying lengths of time were measured. A time-dependent increase was obtained in the amount of acid-liberated FFI and fluorescence. The radioimmunoassay described here had satisfactory reproducibility as judged by the intra-assay precision of 3.4-6.4% and the interassay precision of 7.3-8.9%. The method allows to quantitate FFI on the modified proteins that have been implicated in the complications of diabetes and in normal aging as well.