Glomerular permselectivity: barrier function based on discrimination of molecular size and charge.

Area of Science:

• Nephrology
• Physiology
• Biochemistry

Background:

• Glomerular ultrafiltrate formation depends on pressures, flows, and capillary wall permselectivity.
• The glomerular capillary wall acts as a barrier, excluding macromolecules by size and charge.
• Negative charges in the glomerular wall contribute to its barrier function.

Purpose of the Study:

• To investigate the role of molecular size and charge in glomerular filtration.
• To understand the mechanisms underlying macromolecule exclusion by the glomerular barrier.
• To explore the relationship between glomerular charge properties and kidney injury.

Main Methods:

• Utilized dextran molecules of varying sizes and charges to assess glomerular permeability.
• Examined the influence of molecular radius on filtration of neutral, negatively charged, and positively charged dextrans.
• Correlated findings with morphological studies and known effects of glomerular injury.

Main Results:

• Neutral dextrans <20 A radius crossed freely; >42 A radius were largely excluded.
• Negatively charged macromolecules were more restricted than neutral ones of similar size.
• Positively charged molecules showed enhanced passage compared to neutral polymers.
• Glomerular injury and proteinuria are linked to a loss of charge-selectivity.

Conclusions:

• The glomerular capillary wall possesses both size- and charge-selective properties.
• Fixed negative charges play a crucial role in preventing macromolecule filtration.
• Loss of these negative charges contributes to proteinuria and associated cellular changes in kidney disease.