Figure 3
The Gibbs-Donnan effect. There is a different concentration in the concentration of anionic albumin, which is impermeant, between the vascular (albumin approximately 40 g/L) and the interstitial (albumin approximately 10 g/L) compartments. The negative charges of albumin "attract" cations (largely Na+) into the vascular compartment and "repell" anions (Cl- and HCO3 -) out. Because the concentration of Na+exceeds that of Cl- and HCO3-, "attraction" outweighs "repulsion". Consequently the Gibbs-Donnan effect increases the vascular compartment. The dashed line represents the capillary bed separating the intravascular and interstitial spaces is freely permeable to Na+, K+, Cl-, and glucose.