Urinary excretion of type IV collagen as a specific indicator of the progression of diabetic nephropathy

Aims and Methods: This study was carried out to clarify whether the urinary excretion of type IV collagen (u-IV collagen) detected by specific radioim munoassay, can be used as an indicator for the progression of diabetic neph ropathy. Results: u-IV collagen was higher in diabetic subjects with microa lbuminuria and overt proteinuria than those with normoalbuminuria, IgA neph ropathy, membranoproliferative glomerulonephritis, membranous nephropathy, or control normal subjects, u-IV collagen was positively correlated with se rum and urinary beta(2)-microglobulin and negatively with creatinine cleara nce only in diabetic patients, but not in patients with other glomerular di seases. The serum type IV collagen was not different between all the groups , and not correlated with its urinary excretion. In the advanced diabetic n ephropathy, immunoreactive type IV collagen was detected in glomerular base ment membrane (GBM), tubular basement membrane and Bowman's capsule much mo re than that in the normal kidney. Conclusion: These findings indicated inc reased production and degeneration of type IV collagen in diabetic nephropa thy. It is suggested that augmented turnover of type IV collagen in GEM and tubular basement membrane results in increased concentrations of free u-IV collagen. Therefore, measurement of u-IV collagen may be a useful, specifi c indicator of the progression of diabetic nephropathy. Copyright (C) 2000 S. Karger AG, Basel.