Separation and identification of urinary proteins and stone-matrix proteins by mini-slab sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Mini-slab electrophoresis on sodium dodecyl sulfate/polyacrylamide gel can be used to detect protein in unconcentrated urines containing more than 100 mg of protein per liter. Several urinary proteins--including albumin, transferrin, and the Tamm-Horsfall mucoprotein--precipitate, partly or totally, if urine samples are stored at 4 degrees C for one or two days. The present procedure permits identification of the albumin and transferrin in unconcentrated urines, thus avoiding their partial loss. Stone-matrix proteins in 10 mg or more of urinary calculi also could be detected. Albumin, transferrin, and Tamm-Horsfall mucoprotein accounted for greater than 40% of the total matrix protein in most of the urinary stones analyzed. The precipitation properties of these proteins and their high concentrations in stone matrix relative to those in urine suggest that they may play a role in stone formation and growth.