Alterations in glomerular anionic sites in canine anti-glomerular basement membrane nephritis with onset of severe proteinuria.

Rabbit anti-glomerular basement membrane serum (AGBM) or normal rabbit serum (NRS) were given intravenously (2 ml/kg body weight) to 8 male beagle dogs. Light and transmission electron microscopy and immunofluorescence were performed on the kidneys on day 7 postinjection. Alterations of anionic sites (ASs) of glomerular basement membrane (GBM) in peripheral, proximal, and paramesangial portions were studied quantitatively by electron microscopy using polyethyleneimine (PEI; molecular weight = 1,800) as a cationic probe. Severe or mild proteinuria developed on day 1 and continued until day 6 postinjection. On day 7 after AGBM injection, the number of PEI granules per 1,000 nm length of the lamina rara externa of GBM in all portions was significantly less than that in NRS-treated dogs (10.48 +/- 1.78 versus 14.19 +/- 2.35 granules per 1,000 nm of GBM in peripheral portion, 10.81 +/- 1.91 versus 14.97 +/- 1.35 granules per 1,000 nm of GBM in proximal portion, 8.44 +/- 1.76 vs 13.43 +/- 2.10 granules per 1,000 nm of GBM in paramesangial portion; p < 0.001). These results indicate that a reduction glomerular AS occurs in AGBM-treated dogs in association with severe or mild proteinuria and alterations in glomerular ASs might play an important role in the pathogenesis of proteinuria in the canine anti-GBM nephritis in addition to morphological changes.