Child Kidney Dis.  2015 Oct;19(2):65-70. 10.3339/chikd.2015.19.2.65.

Origin of Proteinuria as Observed from Qualitative and Quantitative Analysis of Serum and Urinary Proteins

• Takahashi

• KMID: 2168404
• DOI: http://doi.org/10.3339/chikd.2015.19.2.65

Abstract

It is well known that proteins present in the primary urine are reabsorbed in the renal proximal tubules, and that this reabsorption is mediated via the megalincubilin complex and the neonatal Fcgamma receptor. However, the reabsorption is also thought to be influenced by an electrostatic interaction between protein molecules and the microvilli of the renal proximal tubules. By analyzing the charge diversity of urinary IgG, we showed that this reabsorption process occurs in a cationic charge-preferential manner. The charge-selective molecular sieving function of the glomerular capillary walls has long been a target of research since Brenner et al. demonstrated the existence of this function by a differential clearance study by using the anionic dextran sulfate polymer. However, conclusive evidence was not obtained when the study was performed using differential clearance of serum proteins. We noted that immunoglobulin (Ig) A and IgG have similar molecular sizes but distinct molecular isoelectric points. Therefore, we studied the differential clearance of these serum proteins (clearance IgA/ clearance IgG) in podocyte diseases and glomerulonephritis. In addition, we studied this differential clearance in patients with Dent disease rather than in normal subjects because the glomerular sieving function is considered to be normal in subjects with Dent disease. Our results clearly showed that the charge-selective barrier is operational in Dent disease, impaired in podocyte disease, and lacking in glomerulonephritis.

Keyword

Charge selectivity; IgG; IgA; Glomerular capillary wall; Charge selectivity index (CSI); Dent disease; Podocyte disease; Nephritis

MeSH Terms

Blood Proteins
Capillaries
Child Health
Dent Disease
Dextran Sulfate
Glomerulonephritis
Humans
Immunoglobulin A
Immunoglobulin G
Immunoglobulins
Isoelectric Point
Microvilli
Nephritis
Podocytes
Polymers
Proteinuria*
Blood Proteins
Dextran Sulfate
Immunoglobulin A
Immunoglobulin G
Immunoglobulins
Polymers