A codiffusing system as a novel model for capillary wall charge selectivity.

The electrostatic interaction associated with polyion-polyion interaction has been thought to be the basis for the differential transport of charged transport probes across the capillary wall. The charge of the transport probe may interact with the negative charges of capillary wall cell surfaces and the intercellular glycocalyx or extracellular matrix. This study has set out to quantitate the exact nature of the polyion-polyion interaction through the theoretical and experimental study of the partition-diffusion of albumin in solutions of anionic polysaccharides (dextran sulfate or heparin) at concentrations up to 250 meq 1(-1) or at an average intercharge distance of 2.2 nm, as compared with solutions of uncharged dextran at the same volume concentration. The results demonstrate that the albumin partition-diffusion is exactly the same in dextran sulfate, heparin and uncharged dextran matrices of the same polymer volume fraction. These results confirm previous studies from this laboratory that the charge effect through polyion-polyion interaction under physiological conditions is negligible.