A model for the glomerular filter.
The model for the glomerular filter presented here is based on the relationship between basement membrane collagen and fibrillar collagen. The glomerular basement membrane collagen is produced by the epithelial cell and present on its surface in a staggered organization as in fibrillar collagen. Binding and aggregation of the collagen molecules with a matrix protein results in a large (+/- 50 nm) meshwork controlled by collagen molecules and bound to the cell surface. Because the matrix proteins bind GAGs, the aggregates are recognizable as anionic sites. A continued production of glomerular basement membrane material will cause a movement towards the endothelial side accompanied with a degradation. This degradation results in a loss of carbohydrates, digesting of alpha-molecules in the triple helices and a loss of anionic sites. The loss of carbohydrates leads to cross-linking and narrowing of the meshes in the direction of the endothelial side of the GBM. Final digestion results in fragmented helices which will pass the GBM and probably be reabsorbed by the epithelial cells or which will pass the slit diaphragm. The slit diaphragm, a staggered collagen structure in plane, functions as a bridge between the epithelial foot processes and is able to regulate the flow and pressure.
D000818:Animals; D001485:Basement Membrane / Q000502:physiology / Q000648:ultrastructure*; D055598:Chemical Phenomena; D002621:Chemistry; D003094:Collagen / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007678:Kidney Glomerulus / Q000502:physiology / Q000648:ultrastructure*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D011347:Procollagen / Q000378:metabolism; D014462:Ultrafiltration
D046911:Macromolecular Substances; D008565:Membrane Proteins; D011347:Procollagen; D003094:Collagen