Effect of steady shear stress on fluid filtration through the rabbit arterial wall in the presence of macromolecules.

1. Transport properties of the arterial wall in general and endothelial cells in particular are known to be sensitive to fluid flow generated shear stress. 2. The effect of steady wall shear stress was studied in vitro on transmural water filtration in the presence of a control perfusate (10 mg/mL bovine serum albumin) and a test perfusate (50 mg/mL Dextran 500). The latter is a macromolecule with certain physical properties comparable to those of the circulating low density lipoproteins. Dextran 500 is a neutral polysaccharide carrying no charge groups. 3. Male rabbits were anaesthetized with sodium pentobarbital and one of the common carotid arteries was cannulated and excised. 4. Fluid flux across the artery wall was measured at a constant transmural pressure (150 cm H2O) in the presence and absence of luminal flow of the perfusate. 5. Luminal flow produced an average increase by 21% in the filtration flux relative to its value under static conditions with 10 mg/mL bovine serum albumin in the perfusate. In the presence of 50 mg/mL Dextran 500 in the perfusate an average reduction by 36% was observed in fluid flux when luminal flow was imposed in the artery. 6. The increase in flux with the control perfusate may be due to a structural alteration of the glycocalyx fibre matrix caused by flow imposed shear stress. The observed decrease in flux with 50 mg/mL Dextran 500 may be accounted for by the deformation of the dextran polymer chains when subjected to shear stress. Although intact molecules are likely to be excluded by the glycocalyx, parts of the chain may insert themselves in the network and enhance the steric exclusion of water. Also, decreased hydration of the medial interstitium may increase medial resistance to fluid transport.