Studies on the glomerular filtration barrier and on the urinary excretion of basement membrane glycoproteins during the accelerated model of nephrotoxic serum nephritis.

A proliferative glomerulonephritis was induced in rats preimmunised with rabbit IgG by injecting a sub-nephrotoxic dose of rabbit anti-rat GBM IgG. All the rats developed a severe proteinuria within 2-5 days after the injection of anti-GBM IgG. At the same time, many mononuclear phagocytes infiltrated the glomeruli, the colloidal iron staining of the glomerular filtration barrier was altered, and the urinary excretion of laminin and of neutral proteinase strongly increased. However, the pattern and intensity of staining of different collagenous and non-collagenous BM glycoproteins were not modified, as shown by indirect immunofluorescence microscopy. The existence of a direct significant correlation between the proteinuria and the laminin urinary excretion, and between the latter and the urinary neutral proteinase activity suggests that lysosomal proteinase of mononuclear phagocytes may be involved in the damage of the GBM during the course of this experimental glomerulonephritis.