Glomerular permeability: transfer of native ferritin in glomeruli with decreased anionic sites

Abstract

Polycations induce loss of fixed anionic sites in the glomerular capillary wall and epithelial changes similar to those reported in proteinuric conditions. To investigate whether such alterations are accompanied by an increase in glomerular permeability, the distribution of anionic ferritin was studied in kidneys perfused with a polycation (protamine sulfate). Cortical biopsies were examined by light and electron microscopy. Glomerular anionic sites were studied by the colloidal iron reaction. In kidneys perfused with protamine, whether or not pretreated with heparin, there was a marked decrease in glomerular polyanion, a flattening and loss of foot processes, and a significant increase in number of ferritin molecules beyond the inner aspect of the glomerular basement membrane, relative to controls. When protamine-treated kidneys were reperfused with heparin, there was restoration of glomerular polyanion, nearly complete reversion of epithelial changes, formation of protamine-heparin complexes in the capillary wall, and a ferritin distribution comparable to that of controls. These results provide additional evidence evidence of the restrictive role of the glomerular polyanion with respect to the filtration of anionic proteins.