Nature of proteinuria in diabetic nephropathy. II- significance of different types of proteinuria in diabetes mellitus

ABSTRACT

The urinary excretion of albumin, alpha 1 acid glycoprotein [1 Ag], IgA and alpha 2 macroglobulin [alpha 2 MG] was determined in 27 diabetics and 8 normal controls using an immunodiffusion technique. Although alpha 1 AG has a molecular weight [40.000] less than that of albumin [69.000], it was detected in the urine of only one third of the diabetics having albuminuria. Its presence in urine of these patients was accounted for by impaired tubular reabsorption. Urinary excretion of IgA was noted at a greater frequency in diabetics with longer duration of diabetes or with a greater impairment of glucose tolerance. This may suggest that the appearance of IgA in urine of diabetics is a refletion of the greater strain imposed on the kidneys by metabolic derrange-ment, or it can be a sign of diabetic nephropathy. alpha 2 MG was detected only in urine of one patient having end stage renal failure. Thus, it is obvious that in diabetic nephropathy, the increased glomerular permeability did not progress readily to allow for the passage of huge macromolecules, such as alpha 2 MG, but remains limited for the passage of relatively smaller proteins such as albumin, though albuminuria is progressive in nature