Comparison of tubular proteinuria, using sodium dodecyl sulphate polyacrylamide gel electrophoresis, in patients during methotrexate or aminoglycoside treatment or with cadmium or Balkan nephropathy.

The pattern of proteinuria found in patients during the administration of methotrexate (MTX) or aminoglycosides (AG) and in cadmium or Balkan nephropathy was investigated using the technique of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). As renal tubular dysfunction increased, measured by the urinary concentration of 4 low molecular mass (LMr) proteins, SDS-PAGE bands appeared in the following order of molecular mass (Mr): 59, 44, 31, then below 31 000. The presence of bands less than 31 000 was not an early indicator of drug-induced renal damage. Tubular proteinuria could be monitored more easily by the serum and urinary measurement of any one of the LMr proteins: alpha-1-microglobulin (alpha 1m), retinol-binding protein (RBP), beta-2-microglobulin (beta 2m), except alpha-1-acid glycoprotein (AGP), than by SDS-PAGE.