Normal filtration action due reabsorption and tubular glomerular filtration membranes, protein in urine (especially smaller molecular weight proteins) little content (daily discharge rate of less than 150 mg), protein qualitative examination when negative. So what is proteinuria, proteinuria is caused by how? When urine increased protein content in ordinary urinalysis can be measured, called proteinuria. If the urine protein ≥3.5g / 24h, then known as proteinuria.
Proteinuria (Proteinuria) is a typical symptom of chronic kidney disease, the causes of proteinuria and glomerular barrier function has a close relationship. Glomerular capillary has three layers, respectively from inside to outside the endothelial cell layer, the base layer and the epithelial cell layer. Since this three cells are distributed filter pore sizes of and negative charge, so glomerular capillary barrier function can be divided into two, namely mechanical barrier - filter pore and charge barrier - a negative charge.
1, the mechanical barrier - the filter holes
Glomerular filtration barrier from the inside out by the three layers:
① endothelial cells lining capillaries. There are many holes on a diameter of 50-100nm endothelial cells, called fenestrae (fenestration). Water, various solutes and protein molecules can freely through the aperture; but can be prevented by blood cells, play a role in blood cell barrier.
② intermediate non-cellular basement membrane, was slightly fibrous network. Plasma larger molecules, such as basement membrane proteins can not. Glomerular basement membrane filtration of macromolecular proteins to prevent major barrier.
③ outer glomerular epithelial cells. Foot process of epithelial cells, the formation of cracks between the intertwined foot processes. There fissure fracture membrane filtration layer (filtration slit membrane), the membrane has a pore diameter 4-14nm, it can prevent from the inside, in two large protein filtered through, is filtered through the last barrier. Endothelial cells, basement membrane and fissures constitute the glomerular filtration membrane. Different filtration pore size of the filtration membrane, can easily make small molecules through the material, and the effective radius of the substance and only through the larger pores, in general, the effective radius of less than 1.8nm substances, can be complete filtration. Effective radius is larger than 3.6nm macromolecules, such as albumin (molecular weight of about 69,000) is almost completely unable filtration.
2, the charge barrier - a negative charge
Filtration membrane containing many layers of negatively charged species, so the filtration membrane permeability also depends on the material to be filtered through the charge. These negatively charged species repels negatively charged plasma proteins, limiting their filtration. Although serum albumin effective radius 3.5nm, but because of its negative charge, it is difficult through the filtration membrane. When various pathological damage (including primary and secondary injury) acts on the kidneys, it can cause damage to the kidneys local microcirculation, promote kidney tissue (functional renal units) ischemia and hypoxia. Because ischemia, anoxia glomerular capillary endothelial cells. Glomerular capillary endothelial cells, once damaged, it will attract circulating inflammatory cell infiltration, and the release of pathogenic inflammatory mediators (IL-1, TNF - α, etc.), can cause pathological damage at this time impaired renal inflammation. In a pathological state kidney glomerular basement membrane (GBM) will be a series of changes: its filtration hole increases or lockout, GBM fracture, charge barrier damage, kidney permeability, filtration membrane negatively charged sugar protein decreased or disappeared, would result in a significant increase compared with the normal negative charge of the plasma protein filtration. Hence the formation of proteinuria in clinical practice.
Viber/WhatsApp:+8615176855086 Skype:live:kidneyservice Email: kidneyservice@hotmail.com
Shijiazhuang Kidney Disease Hospital
Shijiazhuang Kidney Disease Hospital is located in Shijiazhuang city, capital of Hebei Province, which is adjacent to the capital of China, Beijing. It was founded in 1986 and his name has become more widely known in recent decades.....Read More
没有评论:
发表评论