Oncotic pressures opposing filtration across non-fenestrated rat microvessels

R. H. Adamson, J. F. Lenz, X. Zhang, G. N. Adamson, S. Weinbaum, F. E. Curry

Research output: Contribution to journalArticle

205 Citations (Scopus)

Abstract

We hypothesized that ultrafiltrate crossing the luminal endothelial glycocalyx through infrequent discontinuities (gaps) in the tight junction (TJ) strand of endothelial clefts reduces albumin diffusive flux from tissue into the 'protected region' of the cleft on the luminal side of the TJ. Thus, the effective oncotic pressure difference (σΔπ) opposing filtration is greater than that measured between lumen and interstitial fluid. To test this we measured σΔπi across rat mesenteric microvessels perfused with albumin (50 mg ml-1) with and without interstitial albumin at the same concentration within a few micrometres of the endothelium as demonstrated by confocal microscopy. We found σΔπ was near 70% of luminal oncotic pressure when the tissue concentration equalled that in the lumen. We determined size and frequency of TJ strand gaps in endothelial clefts using serial section electron microscopy. We found nine gaps in the reconstructed clefts having mean spacing of 3.59 μm and mean length of 315 nm. The mean depth of the TJ strand near gaps was 67 nm and the mean cleft path length from lumen to interstitium was 411 nm. With these parameters our three-dimensional hydrodynamic model confirmed that fluid velocity was high at gaps in the TJ strand so that even at relatively low hydraulic pressures the albumin concentration on the tissue side of the glycocalyx was significantly lower than in the interstitium. The results conform to the hypothesis that colloid osmotic forces opposing filtration across non-fenestrated continuous capillaries are developed across the endothelial glycocalyx and that the oncotic pressure of interstitial fluid does not directly determine fluid balance across microvascular endothelium.

Original languageEnglish (US)
Pages (from-to)889-907
Number of pages19
JournalJournal of Physiology
Volume557
Issue number3
DOIs
StatePublished - Jun 15 2004

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Tight Junctions
Microvessels
Glycocalyx
Albumins
Pressure
Extracellular Fluid
Endothelium
Water-Electrolyte Balance
Colloids
Hydrodynamics
Confocal Microscopy
Electron Microscopy

ASJC Scopus subject areas

  • Physiology

Cite this

Adamson, R. H., Lenz, J. F., Zhang, X., Adamson, G. N., Weinbaum, S., & Curry, F. E. (2004). Oncotic pressures opposing filtration across non-fenestrated rat microvessels. Journal of Physiology, 557(3), 889-907. https://doi.org/10.1113/jphysiol.2003.058255

Oncotic pressures opposing filtration across non-fenestrated rat microvessels. / Adamson, R. H.; Lenz, J. F.; Zhang, X.; Adamson, G. N.; Weinbaum, S.; Curry, F. E.

In: Journal of Physiology, Vol. 557, No. 3, 15.06.2004, p. 889-907.

Research output: Contribution to journalArticle

Adamson, RH, Lenz, JF, Zhang, X, Adamson, GN, Weinbaum, S & Curry, FE 2004, 'Oncotic pressures opposing filtration across non-fenestrated rat microvessels', Journal of Physiology, vol. 557, no. 3, pp. 889-907. https://doi.org/10.1113/jphysiol.2003.058255
Adamson RH, Lenz JF, Zhang X, Adamson GN, Weinbaum S, Curry FE. Oncotic pressures opposing filtration across non-fenestrated rat microvessels. Journal of Physiology. 2004 Jun 15;557(3):889-907. https://doi.org/10.1113/jphysiol.2003.058255
Adamson, R. H. ; Lenz, J. F. ; Zhang, X. ; Adamson, G. N. ; Weinbaum, S. ; Curry, F. E. / Oncotic pressures opposing filtration across non-fenestrated rat microvessels. In: Journal of Physiology. 2004 ; Vol. 557, No. 3. pp. 889-907.
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