Role of shear and leukocyte adherence on venular permeability in the rat mesentery

The role of fluid shear stress on permeability has been controversial. in v itro studies have shown higher endothelial permeability with an increase in shear, but in vivo higher shear can also decrease permeability by attenuat ing leukocyte adherence (e.g., during an inflammatory response). The potent ial contribution of fluid shear and leukocyte adherence acting simultaneous ly to determine basal levels of permeability remains unresolved. Therefore, the purpose of this study was to understand the effects of basal shear and leukocyte adherence on venular permeability of the rat mesentery. Using a modification of current measurement techniques, we were able to quantify pe rmeability under physiological flow and estimate its convective and diffusi ve components. We found that water filtration plays a minor role in the tra nsport of albumin across venular endothelium, that permeability exhibits a moderately linear correlation with shear, and that the number of leukocytes adherent to the endothelium accounts for the majority of the scatter in th is correlation. Multiple regression analysis of permeability as a function of shear rate and leukocyte adherence revealed significant roles for both f actors (regression P < 0.01, r(2) = 73.9%). (C) 2001 Academic Press.