Glomerular permselection: shape and flow.
The selective permeability of the glomerular basement membrane to macromolecules is a function of the size and charge of the macromolecule. Evidence suggests that shape may also be a factor. The orientation of macromolecules in solution is dependent on their size, shape, and frictional interactions with moving solvent molecules. The spaces between the glomerular visceral epithelial cells (slit pores) may produce a non-uniform distribution of fluid flow within the basement membrane, and this non-uniformity may increase during disease. This report is of a model that relates the filtration of rigid prolate ellipsoidal (cigar) shaped macromolecules to the size and shape of the filter and to the velocity of solvent flow. The calculations, using published macromolecular and glomerular parameters correspond well to published data. The glomerular visceral epithelial cell, by altering the number, size and distribution of the intercellular spaces, may regulate the passage of ellipsoidal shaped macromolecules, such as albumin and IgG, into and through glomerular structures.