title: Persistence of inert macromolecules (Imposil) in the rat mesangium and glomerular functional disturbance.
abstract: Imposil iron-dextran is an inert tracer that has been used to study mesangial uptake and clearance of macromolecular material from the glomerular circulation. Such a tracer may be a useful marker of altered mesangial function in animals with some forms of glomerulonephritis. We have studied mesangial handling of intravenously injected Imposil (50 mg/100 g body weight) in normal rats by light, immunofluorescence and electron microscopy for up to 3 months. Mesangial cell uptake was maximal at 48-54 h. Extrusion and drainage of tracer to the vascular pole and distal tubule was evident at 3 days but iron was still present in mesangial cells at 3 months. Possible functional renal impairment resulting from persistent mesangially sequestered tracer was examined by measuring daily urine protein and iron excretion. A possible relationship between failure of mesangial cells to eliminate inert tracer and increasing glomerular permeability is demonstrated, suggesting that Imposil and similar inert macromolecules cannot be used for long-term studies of mesangial function.
mesh_terms: D000818:Animals; D005920:Glomerular Mesangium / Q000378:metabolism* / Q000503:physiopathology / Q000648:ultrastructure; D005921:Glomerulonephritis / Q000378:metabolism / Q000503:physiopathology; D007501:Iron / Q000652:urine; D007505:Iron-Dextran Complex / Q000378:metabolism*; D007678:Kidney Glomerulus / Q000648:ultrastructure; D046911:Macromolecular Substances; D008297:Male; D008854:Microscopy, Electron; D011507:Proteinuria / Q000209:etiology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D046911:Macromolecular Substances; D007505:Iron-Dextran Complex; D007501:Iron