Increased concentrations of the basement membrane component type IV collagen in sera and urine of diabetics

We measured serum and urinary concentrations of type IV collagen by radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) in diabetics. Serum and urinary concentrations of type IV collagen measured by RIA and ELISA were increased compared to those of control subjects. In diabetics with macroproteinuria or with renal insufficiency, serum and urinary concentrations of type IV collagen were higher than in diabetics without nephropathy or with early renal damage as determined by the presence of microproteinuria. These results suggest that serum and urinary concentrations of type IV collagen are increased in patients with advanced diabetic nephropathy. These increases may indicate that alteration of basement membrane metabolism has occurred in diabetics.