Effects of high molecular weight solutes on fluid flux across the arterial wall

To investigate the mechanisms controlling the flux of plasma proteins into and through the walls of blood vessels, we have studied the effects of two inert protein analogues, Dextran 500 and Poly(ethylene)oxide (PEO) on fluid transport across the walls of intact rabbit common carotid arteries. Transmural fluxes were first measured in vessels pressurized to 150 cmH2O with a solution containing 10 mg/ml albumin alone (control solution) and then with one containing 10 mg/ml albumin plus 10 or 50 mg/ml dextran, or 10 or 30 mg/ml PEO (test solutions). The macromolecule solutions caused a decrease in transmural filtration; the ratios of fluxes with the test solutions to those with the control solutions were 0.89 +/- 0.11 (7), 0.63 +/- 0.08 (8), 0.69 +/- 0.24 (9) and 0.41 +/- 0.09 (4), respectively (Mean +/- SD (n)). These reductions in fluid movement through the vessel wall may be explained quantitatively in terms of the formation of concentration-polarized layers of the macromolecules at the luminal surface or interactions of the macromolecules with the endothelial glycocalyx, causing a decrease in its permeability.