[Electron microscopic study of the glomerular basement membrane charge barrier and the charge of immune deposits in lupus nephritis].

In order to evaluate the pathogenesis of proteinuria and the charge of immune deposits in lupus nephritis, anionic sites of periodate-lysin-paraformaldehyde (PLP) fixed renal tissue (5 patients with renal pelvic tumor as normal control and 17 patients with lupus nephritis), were stained with the critical electrolyte concentration method. Cuprolinic blue (CB) was used as a cationic probe. Ultra-structural study and semi-quantitative analysis were done. In the normal glomerular basement membrane (GBM), the CB stainable anionic sites appeared as filamentous structure with several short lateral branches. On the basis of electron microscopic observation of isolated proteoglycan, it is suggested that the central filaments are the protein core and the branches are the glycosaminoglycans of proteoglycan molecules. These filamentous anionic sites were located mainly in the laminae larae and lie close to each other forming a mesh-like network pattern. The semi-quantitative analysis of the normal GBM revealed that the number of anionic sites in the lamina rara externa (LRE) was 22.9 +/- 1.9-23.7 +/- 1.4/1000 nm GBM and in the lamina rara interna (LRI) 14.0 +/- 1.6-15.1 +/- 1.5/1000 nm GBM. These findings suggest that the anionic sites composed of heparan sulphate proteoglycan occupy large area of the laminae larae and prevent permeation of anionic molecules. In non-proteinuric 5 patients with class II lupus nephritis, the number of anionic sites of the GBM (LRE; 21.3 +/- 2.0-22.3 +/- 1.8/1000 nm GBM, LRI; 13.5 +/- 2.0-14.2 +/- 2.0/1000 nm GBM) showed no significant difference from that of the normal GBM. In contrast, the GBM of proteinuric patients with class IV (6 patients, LRE; 14.8 +/- 2.7-19.3 +/- 1.8/aooo nm GBM, LRI; 5.8 +/- 1.9-11.3 +/- 2.4/1000 nm GBM) and (V) (6 patients, LRE; 13.0 +/- 2.4-17.9 +/- 2.8/1000 nm GBM, LRI; 12.0 +/- 1.9-13.0 +/- 2.5/1000 nm GBM) exhibited loss of the anionic sites in association with the localization of the immune deposits (ID). From these findings, it is concluded that in severe and active lupus nephritis the failure of charge barrier of the GBM is responsible for the proteinuria. The ID observed in the patients with lupus nephritis were not stained with CB. This finding suggests that net charge of the ID could be cationic and that cationic immune complex and/or antibody could involve in the pathogenesis of lupus nephritis.