A map of urine proteins based on one-dimensional SDS-polyacrylamide gel electrophoresis and Western blotting using one microliter of unconcentrated urine

Abstract

A sensitive one-dimensional SDS-polyacrylamide gel electrophoretic system was devised whereby the proteins in 1 [mu]l of unconcentrated urine could be visualized by silver staining over the range 9 000-900 000 molecular weight. Identification of urine proteins was confirmed by Western blotting using peroxidase labelled antibodies. A map of the major proteins visualized in urine from individuals with renal disease was constructed. We conclude that the information available from the simple analysis of proteins according to their size is limited to general conclusions regarding whether proteinuria is likely to be of tubular or glomerular or mixed origin. More specific identification of individual proteins is not feasible because simple protein staining is not sufficiently reliable to identify individual proteins. The reasons for this conclusion are as follows: (a) many proteins in urine migrate with similar apparent molecular weights, (b) some proteins are not visualized by silver staining, and (c) albumin polymeric complexes and fragments can be present at almost any molecular weight. However, one-dimensional SDS-polyacrylamide gel electrophoresis together with Western blotting does provide reliable information which might be clinically and experimentally useful.