Importance of sodium dodecyl sulfate pore-graduated polyacrylamide gel electrophoresis in the differential diagnostic of Balkan nephropathy.

Balkan nephropathy (BN) is an endemic disease, which leads to end-stage renal failure and artificial renal replacement therapy. Pathologically it is characterized by progressive interstitial nephritis in a large population of villages situated in the proximity of a bend of the Danube up to a distance of 100 km from the river in several parts of Bulgaria, Romania, and the former Yugoslavia. The urinary proteins of 19 patients with BN from the region of Vratza, Bulgaria were examined using ultrathin layer sodium dodecyl sulfate (SDS) pore-graduated polyacrylamide gel electrophoresis (PAGE) and silver staining. The documentation of urinary proteins pattern was performed using laser densitometry and consecutive electronic processing for the purpose of characterizing and quantifying protein excretion. Our results show that the proteinuria of BN is predominantly tubular, consisting of low molecular weight species (10-65 kilodaltons). The amount of tubular protein changes with the progression of the disease. SDS-polyacrylamide gel electrophoresis (PAGE) is a diagnostic method for early diagnosis of tubular failure in BN. Using our method of SDS-PAGE, tubular failure can be detected even at a total protein concentration below 0.1 g/L and when the serum creatinine concentration is normal. Additionally, our method of SDS-PAGE supports the differentiation of BN from glomerular disease.