BACKGROUND: The beta-d-endoglycosidase, heparanase, is emerging as an important contributor to the pathogenesis of proteinuria. The purpose of the present study therefore was to examine the role of heparanase in a model of accelerated anti-glomerular basement disease (anti-GBM). METHODS: Accelerated anti-GBM disease was induced and animals sacrificed at day 10 to establish heparanase expression using immunohistochemistry and western blot analysis. In addition, cortex was isolated from normal and diseased glomeruli to determine if mRNA levels altered with disease. A previously validated anti-heparanase antibody associated with proteinuria reduction, in a model of membranous nephropathy, was administered prior to disease induction to establish its impact on protein excretion in this model. RESULTS: At day 10 of anti-GBM disease, an increase in glomerular heparanase was shown using immunohistochemistry. Sequential staining studies revealed that this increase was associated with glomerular endothelial, epithelial cells and invading ED-1-positive inflammatory cells. RT-PCR revealed an insignificant 1.2-fold induction of mRNA at day 10 of disease. Western blot analysis of kidney cortex confirmed that the active 58-kDa heparanase species was restricted to diseased kidney at day 10. The inactive 65-kDa precursor, however, was found only in cortex derived from normal kidney. Proteinuria at day 10 of disease was significantly reduced, in the absence of altered rat anti-sheep antibody titres, after administration of a validated polyclonal anti-heparanase antibody (P < 0.05). Furthermore, sheep IgG deposition was not altered by administration of the anti-heparanase antibody. CONCLUSION: These data suggest that heparanase contributes to the pathogenesis of proteinuria in a model of anti-GBM disease.