Is There a Coupling of Protein Transport to the Rate of Transcapillary Filtration?
In practically all previous lymphatic protein flux analysis a coupling of large solute transport to transcapillary volume flow has been demonstrated. This seems to hold even for macromolecules as large as fibrinogen, IgM and LDL [7, 8, 14, 49]. In the study by Rippe et al. [48] mentioned above, there was, indeed, a clear-cut coupling of albumin transfer to transcapillary filtration rate, the coupling coefficient being of the order of 0.06–0.08, which corresponds to an albumin reflection coefficient (σalb) of 0.92–0.94 (fig. 4). Furthermore, somewhat surprisingly, the clearance (Cl) of RISA during isogravimetric conditions, proved to be dependent upon the plasma (perfusate) colloid osmotic pressure (πp). Since ‘clearance’ represents the rate of mass transfer divided by the plasma (tracer) concentration, it should be completely independent of the plasma protein level. However, the dependence of Cl upon πp can be understood if the concept of ‘volume recirculation’ in heteroporous membrane
