SEM of complement-independent nephrotoxic nephritis.

Complement-independent nephritis was induced in rats by intravenous injections of duck anti-rat nephrotoxic serum (DNTS). The kidneys were examined by light and immunofluorescent microscopy, plus electron microscopy (SEM and TEM) at 15, 30 and 60 minutes and on days 1 and 5. Additional experiments included pretreatment with heparin sulfate prior to DNTS and perfusion experiments 24 hours following DNTS using normal saline and heparin sulfate. Light microscopy demonstrated no increase in inflammatory cells. Immunofluorescent microscopy showed only linear staining against duct anti-rat immune globulin. TEM and SEM showed glomerular capillary wall changes at 24 hours which correlated roughly with the level of proteinuria and varied from minimal changes, grade I, to severe foot process effacement and partial detachment of endothelium and epithelium, grade III. Pretreatment with heparin sulfate exaggerated the severity of the Grade III changes. Perfusion of DNTS rats with normal saline result in detachment of loosened podocytes. Perfusion of DNTS rats with heparin sulfate resulted in severe podocyte detachment. Examination of DNTS rats on day 5 revealed reversion to normal structure. SEM and TEM complemented each other in demonstrating the unusual DNTS induced phenomenon of weakened cell attachment unrelated to classical complement and inflammatory cellular mechanisms.