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Quantifying Glomerular Permeability of Fluorescent Macromolecules Using 2-Photon Microscopy in Munich Wistar Rats
Published on: April 17, 2013
Quantifying glomerular permeability of fluorescent macromolecules using 2-photon microscopy in Munich Wistar rats
Ruben M Sandoval1, Bruce A Molitoris
1Medicine/Nephrology, Indiana University School of Medicine.
Journal of Visualized Experiments : Jove
|May 1, 2013
Summary
New research reveals proximal tubule cells (PTCs) retrieve filtered albumin, challenging traditional views of kidney filtration barriers. This highlights PTCs
Area of Science:
- Nephrology
- Renal Physiology
- Molecular Biology
Background:
- Kidney diseases causing protein loss are linked to filtration barrier defects (podocytes, endothelial cells, basement membrane).
- Traditional methods suggested minimal albumin in tubular fluid, implying a near-impermeable barrier.
Purpose of the Study:
- To detail a technique for in vivo visualization and quantification of glomerular albumin permeability.
- To investigate albumin filtration and reabsorption by proximal tubule cells (PTCs).
Main Methods:
- Intravital 2-photon microscopy to visualize fluorescent albumin in the kidney.
- Quantification of albumin filtration into Bowman's space.
- Assessment of albumin reabsorption and transcytosis by PTCs.
Main Results:
- Direct visualization confirmed albumin filtration across the glomerular filtration barrier (GFB).
- Proximal tubule cells (PTCs) efficiently reabsorb filtered albumin via transcytosis.
- Similar permeability was observed for dextran polymers of similar size to albumin.
Conclusions:
- The glomerular filtration barrier is more permeable to albumin than previously assumed.
- Proximal tubule cell (PTC) albumin reabsorption is a critical component of renal protein homeostasis.
- Proteinuric kidney diseases may involve dysregulation of PTC albumin reclamation.
