PMID: 6399307Jan 1, 1984Paper

Distribution of body fluids: local mechanisms guarding interstitial fluid volume

Journal of Physiology, Paris
K Aukland

Abstract

The plasma volume is determined by fluid influx through drinking and outflux by renal excretion. Both fluxes are regulated according to plasma volume and composition through arterial pressure, osmoreceptors and vascular stretch receptors. As to the remaining part of the extracellular volume, the interstitial space, there is no evidence that its volume (IFV), pressure or composition are sensed in such a way as to influence water intake or excretion. Nevertheless, IFV is clearly regulated, often pari passu with the regulation of plasma volume. However, there are many exceptions to parallel changes of the two compartments, indicating the existence of automatic, local mechanisms guarding the net transfer of fluid between plasma and interstitium. Thus, a rise in arterial and/or venous pressure, tending to increase capillary pressure and net filtration, is counteracted by changes in the "Starling forces": hydrostatic and colloid osmotic pressures of capillary blood and interstitial fluid. These "oedemapreventing mechanisms" (A. C. Guyton) may be listed as follows: Vascular mechanisms, modifying capillary pressure or interstitial fluid pressure (IFP). Increased transmural vascular pressure elicits precapillary constriction and thereby...Continue Reading

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