Modeling the adaptive permeability response of porcine iliac arteries to acute changes in mural shear.
The hypothesis that much of the uptake of macromolecules by the vascular wall takes place while the endothelial lining is adapting to changes in its hemodynamic environment is being tested by a series of in vivo measurements of the uptake of Evans-blue-dye-labeled albumin by porcine iliac arteries subjected to acute changes in blood flow. The uptake data are interpreted through an ad hoc model of the dynamic permeability response that is proposed to accompany alterations in mural shear. The model is able to correlate, with a single set of parameters, the vascular response to a variety of experimental protocols, including sustained step increases and decreases in shear, and alternations in shear of various periods. The best-fit parameters of the model suggest that the adaptive response to an increase in shear proceeds with a latency of approximately 1.5 min and a time constant of approximately 90 min that is substantially shorter than the response to a decrease in shear.