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, 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<0.05) and ₂-microglobulin excretion (P<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.