Document Detail

Glomerular filtration into the subpodocyte space is highly restricted under physiological perfusion conditions.
MedLine Citation:
PMID:  17715264     Owner:  NLM     Status:  MEDLINE    
Production of urine is initiated by fluid and solute flux across the glomerular filtration barrier. Recent ultrastructural studies have shown that under extreme conditions of no filtration, or very high filtration, a restriction to flow is predicted in a space underneath the podocyte cell body or its processes, the subpodocyte space (SPS). The SPS covered up to two-thirds of the glomerular filtration barrier (GFB) surface. The magnitude of this restriction to flow suggested that it might be unlikely that filtration into and flow through the SPS would contribute significantly to total flow across the entire GFB under these conditions. To determine whether the SPS has similar properties under normal physiological conditions, we have carried out further three-dimensional reconstruction of rat glomeruli perfused at physiologically normal hydrostatic and colloid osmotic pressures. These reconstructions show that the sub-podocyte space is even more restricted under these conditions, with a mean height of the SPS of 0.34 microm, mean pathlength of 6.7 +/- 1.4 mum, a mean width of the SPS exit pore of 0.15 +/- 0.05 microm, and length of 0.25 +/- 0.05 microm. Mathematical modeling of this SPS based on a circular flow model predicts that the resistance of these dimensions is 2.47 times that of the glomerular filtration barrier and exquisitely sensitive to changes in the dimensions of the SPS exit pore (SEP), indicating that the SEP could be the principal regulator of the extravascular pressure in the SPS. This suggests a physiological role of the podocyte in the regulation of glomerular fluid flux across most of the GFB.
Christopher R Neal; P Robert Muston; David Njegovan; Rebecca Verrill; Steven J Harper; William M Deen; David O Bates
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-08-22
Journal Detail:
Title:  American journal of physiology. Renal physiology     Volume:  293     ISSN:  1931-857X     ISO Abbreviation:  Am. J. Physiol. Renal Physiol.     Publication Date:  2007 Dec 
Date Detail:
Created Date:  2007-11-28     Completed Date:  2008-02-07     Revised Date:  2011-04-28    
Medline Journal Info:
Nlm Unique ID:  100901990     Medline TA:  Am J Physiol Renal Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  F1787-98     Citation Subset:  IM    
Dept. of Physiology, Univ. of Bristol, Southwell St., Bristol BS2 8EJ, UK.
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MeSH Terms
Glomerular Filtration Rate
Image Processing, Computer-Assisted
Kidney / cytology,  metabolism*,  ultrastructure
Kidney Glomerulus / cytology,  metabolism,  physiology*
Models, Statistical
Osmotic Pressure
Podocytes / physiology*,  ultrastructure
Rats, Inbred WKY
Grant Support
69049//Wellcome Trust
Reg. No./Substance:

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