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A new view of Starling's hypothesis at the microstructural level.
1Department of Mechanical Engineering, The City College of The City University of New York, New York, New York 10031, USA.
Microvascular Research
|October 21, 1999
Summary
This study redefines Starling forces, proposing the endothelial surface glycocalyx acts as the primary molecular sieve. This suggests capillary filtration is lower than previously thought, potentially eliminating the need for venous reabsorption.
Area of Science:
- Physiology
- Biophysics
- Cell Biology
Background:
- The traditional Starling forces model assumes global pressure differences across capillary walls.
- Previous models did not fully account for the role of the endothelial surface glycocalyx in protein filtration.
Purpose of the Study:
- To quantitatively investigate the hypothesis that Starling forces are determined by local pressure differences across the endothelial surface glycocalyx.
- To propose the glycocalyx as the primary molecular sieve for plasma proteins.
Main Methods:
- Development of a spatially heterogeneous microstructural model.
- Quantitative investigation of transient and steady-state experiments on frog mesentery capillaries.
Main Results:
- The model explains oncotic absorption in transient states and filtration in steady states.
- Predicts significant local protein concentration differences behind the glycocalyx.
- Indicates convective protein flux impedes back diffusion.
Conclusions:
- The endothelial surface glycocalyx is the primary molecular sieve, not the capillary wall globally.
- Capillary filtration is significantly lower than previously estimated.
- Venous reabsorption may not be necessary under these revised principles.