Biology of glomerular podocytes
- Pierre Ronco, MD, PhD
Pierre Ronco, MD, PhD
- Professor of Renal Medicine
- Pierre et Marie Curie University, France
- Section Editors
- Richard J Glassock, MD, MACP
Richard J Glassock, MD, MACP
- Editor-in-Chief — Nephrology
- Section Editor — Glomerular Diseases
- Emeritus Professor
- The David Geffen School of Medicine at UCLA
- Brad H Rovin, MD
Brad H Rovin, MD
- Section Editor — Glomerular Diseases
- Professor of Medicine and Pathology
- The Ohio State University College of Medicine
The healthy kidney filters metabolic byproducts into the urine but prevents the passage of albumin and other larger essential molecules. This selective filtration occurs across the glomerular capillary wall:
●Under normal circumstances, the glomerular capillary wall is extremely permeable to water and small solutes, but negligibly to albumin or other proteins of equivalent molecular weight or larger.
●Defects in the glomerular capillary wall result in increased permeability to albumin and proteins of similar size or even larger, causing proteinuria.
●Electrical potential differences generated by transglomerular flow may modulate the flux of anionic (charged) albumin across the glomerular capillary wall .
The traditional view that the glomerular capillary wall hinders the transit of protein is largely based upon micropuncture studies that demonstrated very low concentrations of albumin in Bowman's space in non-nephrotic animals [2,3]. This view has been challenged by newer data that have demonstrated by intravital 2-photon microscopy, much higher concentrations of albumin in Bowman's space than were reported previously . Given the novelty of the technique of intravital 2-photon microscopy, these observations need to be validated in other systems and species, especially since they substantially alter our understanding of the pathogenesis of proteinuria [5-7].
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