The effect of varying albumin concentration of the hydraulic conductivity of the rabbit common carotid artery

Rabbit common carotid arteries were cannulated in situ, after ligation of their branches, and transferred to a perfusion apparatus in such a way that they were maintained at their physiological dimensions and the endothelium remained intact. The vessels were pressurized to 150 cm H 2O with Krebs solution and the wall smooth muscle was relaxed with 10 −4 M NaNO 2. The rate of inflow of perfusate into the vessels was measured by following the movement of a bubble in a calibrated capillary which, when steady, was taken to indicate the transmural filtration rate. The filtration rate was 1.48 ± 0.26 × 10 −6 cm sec −1 (11) (mean, SD, n) with 1 g/dl bovine serum albumin in Krebs solution. The values with 0, 4, 7, and 10 g/dl, normalized by the 1 g/dl value were 1.38 ± 0.16 (7), 0.80 ± 0.05 (9), 0.65 ± 0.03 (8), and 0.47 ± 0.06 (9), respectively. The hydraulic conductivity of the wall was also found to depend on perfusate albumin concentration. The 1 g/dl value was 0.92 ± 0.17 × 10 −8 cm sec −1 (cm H 2O) −1 (11) and the values with 0, 4, 7, and 10 g/dl normalized by the 1 g/dl value were 1.35 ± 0.16 (7), 0.87 ± 0.06 (9), 0.81 ± 0.03 (8), and 0.72 ± 0.06 (9), respectively. The findings were analyzed in relation to models involving interaction of albumin with the endothelial glycocalyx, concentration polarization at the blood/wall interface, dependence of flux on solvent viscosity and dependence of the porosity of the wall interstitium on solvent flux. Both concentration polarization and variation of the porosity of the wall interstitium provide reasonable quantitative explanations for the findings.