Rapid differentiation of glomerular and tubular proteinuria by sodium dodecyl sulfate polyacrylamide gel electrophoresis

Serum and urine protein samples were incubated with sodium dodecyl sulfate and subjected to polyacrylamide gel electrophoresis. There was a linear relationship between the logarithm of the molecular weight of the protein and its distance of migration (R_F) on the gel. This relationship held over a molecular weight range from at least 160000 to 12000, i.e., over a range particularly useful for serum proteins and urine proteins. This system was then applied to the analysis of both serum and urine proteins. Glomerular proteinuria (characterized by the presence of albumin and plasma proteins of a molecular size larger than albumin) and tubular proteinuria (characterized by the presence of albumin and proteins of molecular size smaller than albumin) were readily distinguished. The results were similar to those obtained on the same samples with Sephadex G-200 and Sephadex G-75 columns. The SDS polyacrylamide gel electrophoretic method resolved the proteins of varying molecular weights better than did Sephadex. It was simple to use, and very much more rapid; thus, it was suitable for the examination of large numbers of samples.