Why Massive Proteinuria Appear in Nephrotic Syndrome

The emergence of proteinuria to the person's body is very bad,Why Massive Proteinuria Appear in Nephrotic Syndrome?
Influence of size of protein molecule. Glomerular capillary’s elimination of a certain substance is in inverse proportion to its effective molecular radius, so the larger the molecular weight, the less of it will be filtered out or just cannot be filtered out at all.

In general condition, less amount of plasma protein (for example, albumin) with 60~70 thousand Dalton molecular weight will be filtered out; plasma protein (for example, α1 lipoprotein) of which the molecular weight is more than 200 thousand Dalton cannot be filtered out while plasma protein with relatively small molecular weight (less than 40 thousand) such as muramidase, β2-mg and light chain of immune globulin etc. can be filtered out freely. The barrier function, of which the filtration varies with protein molecular weight, is called molecule-selective barrier (or mechanical barrier).

Why does massive protein appear in Nephrotic Syndrome? Another reason is that protein is electrically charged. Both the endothecium and exothecium of the glomerular basement membrane and the surface of endothelial and epithelial cells of the glomerular vascular loops as well as the mesangial membrane contain rich amount of glycosaminoglycan (heparin sulfate) and sialic acid, both of which can charge the glomerular filtration membrane with negative charge and form the electrostatic barrier. By principle of “like charges repel”, clearance rate of protein with negative charges is the lowest and protein with positive charges the highest.