Microheterogeneity of urinary albumin and tubular proteinuria in juvenile diabetes mellitus.

We studied differential urinary albumin excretion by a double one-dimensional gel electrophoresis with decyl sodium sulphate-polyacrylamide gel electrophoresis in the first, and isoelectric focusing in the second dimension in 37 diabetic children and 20 healthy subjects. In addition, total proteins, albumin, beta 2-microglobulin and molecular size distribution of urinary proteins were measured, the latter using sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Whilst albuminuria was not significantly different from controls we found an increased microheterogeneity of urinary albumin in 38% of patients. In addition, low molecular weight protein (P less than 0.05) and beta 2-microglobulin excretion (P less than 0.01) were elevated. It is suggested that the appearance of highly heterogenous albumin in the pI range of 5.3-5.9 is the result of a decreased tubular reabsorption.