Variability in Microvascular Estimates of Capillary Surface Area for Exchange
A recurring and tantalizing deficiency in many areas of microvascular research is the problem of quantitative reconciliation of measurements made in whole organs (or whole animals) versus those made at the level of individual microvessels. With respect to endothelial cell function, it is recognized that whole organ measurements of capillary filtration coefficient yield values that are 10–20 times lower than single vessel permeability measurements,1 and that observed transport rates of macromolecules in experimental systems at low volume flows exceed calculations based on the two pore model.2 It is clear that at least a partial contribution to these discrepancies lies in the assumptions underlying the models or experimental systems. For example, comparison of data collected by whole organ versus single vessel approaches depends on how ‘typical’ is the single vessel selected for measurement, or on assumptions describing heterogeneity of function in the whole organ approach.
KeywordsCapillary Density Single Vessel Capillary Blood Flow Cremaster Muscle Functional Capillary Density
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