Proteinuria and progression of chronic kidney disease. Does the kind of excreted protein affect progression of renal disease?

Abstract

Massive proteinuria in the case of glomerular disease is an effect of deragements in filtration barrier and disorders of proteins resorption (concerning mainly low-molecular proteins) by the epithelial cells of proximal tubules. The barrier’s permeability is selective and depends on the size of the molecules in the plasma and their charge. The growing intensity of disorders of structural integrity of glomerular capillary walls is accompanied not only by the increased amount of proteins; proteins of larger molecule radius and larger molecular weight appear in the tubular lumens; the selectivity of the filtration barrier is disturbed. Initially, selective proteinuria appears, with albumin (molecular weight - 69 kD, molecular radius - 36 Å) as the dominant protein. With increasing damage to the glomeruli, a growing amount of proteins with greater molecular weight gets through the capillary walls and the amount of, e.g., IgG (molecular weight - 150 kD, molecular radius - 55 Å) in the tubular lumen increases rapidly. It has been believed for a long time that the sort of excreted proteins can be a better indicator of the damage to the glomerular capillary walls than the total protein excreted with urine; it can also affect the response to treatment and prognostication for patients with proteinuria. We would like to discuss the problem in this paper.