Reactivity with diazonium salts of albumin from micro and macroalbuminuric diabetic patients.

A recent theory of the pathogenesis of diabetic microalbuminuria points to an involvement of glycated albumin, which has been demonstrated as being able to fluetrate the renal filter. The chemical characterization of urinary albumin, initially performed on the electrical charge and conformation of the protein has now been extended to the affinity properties for specific chemical probes. In this context, urinary albumin from Albustix-negative diabetic patients was found to be highly reactive towards diazonium salts (a dye specific for pyrrole rings) while the same protein purified from macroproteinuric diabetics showed no difference in reactivity towards diazonium salts compared to serum or normal albumin. These data indicate that, beside being highly anionic and conformationally deranged, urinary albumin in conditions of normal renal selectivity contains pyrrole structures. The reasons for considering this reactivity as an indirect sign of rearranged structure are presented here.