Ultrastructual alterations of glomerular anionic sites in idiopathic membranous glomerulonephritis

Abstract

The relation of ultrastructual alterations of glomerular anionic sites to morphological changes of the glomerular basement membrane (GBM) was studied in biopsies in idiopathic membranous glomerulonephritis (MGN) using polyethyleneimine (PEI) as a cationic probe. The subepithelial deposits did not fix PEI, and only a very few anionic sites were found between subepithelial deposits and adjacent epithelial cells. Thus, anionic sites of the lamina rara externa (LRE) were markedly decreased in number and interrupted by subepithelial deposits in the earlier stages (stage I and II). As the deposits were incorporated into the GBM in the later stage (stage III), the anionic sites of the LRE were restored by a covering of newly formed GBM. A marked loss of the negative charge on the epithelial cell surface coat (ESC) covering the deposits and foot process effacement were persisted during the course of the disease. The anionic sites of the lamina rara interna (LRI) appeared much less altered in any stage of MGN. These findings suggest that subepithelial deposition of immune reactants is associated with focal loss and disorganization of anionic sites on the GBM, resulting in the glomerular barrier function defect.