Platelet-activating factor alters glomerular barrier size selectivity for macromolecules in rats

Area of Science:

• Nephrology
• Renal Physiology
• Molecular Pharmacology

Background:

• Platelet-activating factor (PAF) is a potent lipid mediator implicated in various physiological and pathological processes.
• Understanding PAF's role in glomerular function is crucial for developing targeted therapies for kidney diseases.

Purpose of the Study:

• To investigate the impact of PAF on glomerular permeability to macromolecules in isolated perfused rat kidneys.
• To elucidate the mechanisms underlying PAF-induced changes in kidney function, including the role of calcium ions.

Main Methods:

• Isolated perfused rat kidneys were used to assess protein excretion and fractional clearance of dextrans of varying sizes.
• Experiments involved infusion of PAF, a PAF receptor antagonist (L 652731), and varying extracellular calcium concentrations.

Main Results:

• PAF infusion significantly increased protein excretion and the fractional clearance of large dextrans, indicating altered glomerular permeability.
• These effects were reversible upon cessation of PAF infusion and were completely blocked by a specific PAF receptor antagonist.
• Reduced extracellular calcium concentration markedly attenuated PAF-induced proteinuria.

Conclusions:

• PAF induces a reversible increase in glomerular permeability to macromolecules in isolated perfused kidneys.
• PAF's action involves enhancing the transmural passage of large molecules, a process dependent on extracellular calcium.
• These findings highlight PAF as a key mediator in modulating kidney permselectivity and suggest calcium's critical role in this process.