Effect of periodic alterations in shear on vascular macromolecular uptake

Experiments were carried out in swine to test the hypothesis that changes i n the fluid dynamic environment of the arterial wall, with time constants o f several minutes to perhaps a few hours, prompt adaptive responses that tr ansiently increase endothelial permeability. After parenteral Evans Blue Dy e (EBD) administration, the hemodynamics of the external iliac arteries of the experimental animals were altered using a reversible arteriovenous femo ral shunt. For 3 h, the shunt was opened and closed with a period (tau) bet ween 1-180 min. Subsequently, the animal was euthanized and the iliac vesse ls were photographed en face to obtain the distribution of EBD-bound albumi n uptake by the tissue during its exposure to the dye. Albumin uptake incre ases with tau in a fashion that can be explained by an a priori model of th e adaptive permeability response, with a time constant of about an hour.