Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the capacity of a blood vessel wall to allow for the flow of small molecules (drugs, nutrients, water, ions) or even whole cells (
lymphocytes on their way to the site of
inflammation) in and out of the vessel.
Blood vessel walls are lined by a single layer of
endothelial cells. The gaps between endothelial cells (
cell junctions) are strictly regulated depending on the type and physiological state of the tissue.[1][2][3][4]
There are several techniques to measure vascular permeability to certain molecules. For instance, the cannulation of a single microvessel with a micropipette, the microvessel is perfused with a certain pressure, occluded downstream and then the velocity of some cells will be related to the permeability.[5][6] Another technique uses multiphoton fluorescence intravital microscopy through which the flow is related to fluorescence intensity and the permeability is estimated from the Patlak transformation. [7]
^Michel, C. C., Mason, J. C., Curry, F. E. & Tooke, J. E. Development of Landis Technique for Measuring Filtration Coefficient of Individual Capillaries in Frog Mesentery. Q J Exp Physiol Cms 59, 283-309 (1974).
^Bates, D. O. & Harper, S. J. Regulation of vascular permeability by vascular endothelial growth factors. Vascul Pharmacol 39, 225-237 (2002)
^Patlak, C. S., Blasberg, R. G. & Fenstermacher, J. D. Graphical evaluation of blood-to-brain transfer constants from multiple-time uptake data. J Cereb Blood Flow Metab 3, 1-7 (1983).
^Page, RC; Schroeder, HE. "Pathogenesis of Inflammatory Periodontal Disease: A Summary of Current Work." Lab Invest 1976;34(3):235-249