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The main function of human kidneys is to filter blood and remove metabolic waste while retaining the normal blood composition and volume. The first step of this process is blood filtration through glomerular capillary wall; a membrane consists of multiple layers: endothelium cell layer, the glomerular basement membrane (GBM) and the epithelial foot processes with their interconnecting slit diaphragm. This work focuses on a hydrodynamic model describing hindered transport of electrically neutral macromolecules through the slit diaphragm and the glomerular basement membrane (GBM). The glomerular basement membrane was modeled as a medium consisting of two fibers, collagen type IV and glycoaminoglycan, whereas the epithelial slit was modeled as a row of parallel cylindrical fibers. The non-uniform cylinder spacing is assumed to follow the gamma distribution. The mean value of the spacing and its standard deviation are calculated from the experimentally obtained hydraulic permeability using the Newton-Raphson's method. The averaged sieving coefficients through the slit diaphragm are calculated by using this distribution function and are combined with the sieving coefficients through GBM to find total sieving coefficients. Results are found to agree very well with total sieving coefficients of Ficoll solutes obtained experimentally. Effects of physiological change observed in patients with membranous nephropathy on glomerular size-selectivity are also investigated.
