Analysis of Transvascular Transport Phenomena in the glomerular and peritoneal microcirculation

Abstract: The current work is devoted entirely to the study of passive transport phenomena, or more specifically, the more simple diffusion, electric migration and filtration of solute matter and water over glomerular and peritoneal capillary walls. The driving forces behind such trans-capillary transport phenomena have long been assumed to be simple gradients of concentration, hydrostatic pressure and electric potential. Despite decades of research, the relative importance of these different transport mechanisms remains a highly controversial subject. In Study I we explore the subject of charge selectivity in the glomerular filtration barrier (GFB). The results of this study indicate that electrical charge may be of less importance in the hindrance of charged molecules in the GFB than previously thought.In Study II, we construct a distributed two-pore model and use it to analyze experimental data (θ vs. SE-radius). The results indicate that the wide distribution obtained in the data analysis may be due to a variation in solute size rather than a true variation in pore size. In addition, several theoretical results are presented such as Poiseuille’s law for a distributed pore population. Study III: One of the many unresolved questions regarding the GFB is the reason behind the marked difference in permeability between albumin and Ficoll. In this study, the distributed two-pore model is extended by introducing size distributions on the solute molecules. Experimental data from the rat glomerulus and from precision-made nanopore membranes are analyzed. We show that a variation of only 16% in the size of the solute molecule is sufficient to explain the difference in permeability between albumin and Ficoll. Study IV: The three-pore model is a widely applied model of peritoneal dialysis. Here an extended version of the classical model is used to optimize automated peritoneal dialysis for a wide range of different scenarios. The results show that large reductions (>20%) in glucose absorption are possible by using optimized (bi-modal) regimes.