Scanning electron microscopy of the kidney glomerular epithelium after treatment with polycations in situ and in vitro

Changes in fine structure of glomerular epithelial cells (podocytes) were examined after treatment in situ and in vitro with polycations (i.e., protamine sulfate and poly-1-lysine). Scanning and transmission electron microscopic observations indicate that polycation-induced alterations of the glomerular epithelium are similar in many respects to those resulting from puromycin aminonucleoside nephrosis. These alterations include the formation of junctional complexes between adjacent podocyte processes, flattening and retraction of podocyte processes, extensive folding of the slit diaphragms, formation of interpedicular microbridges, and development of irregular knobby surface-microprojections. Prolonged treatment in vitro with high concentrations of polycations results in nearly complete loss of podocyte processes and the transformation of these once elaborate cells into simple polyhedral cells. The foregoing observations support the view that pedicel loss in puromycin aminonucleoside nephrosis may be due to a reduction in the glomerular epithelial polyanionic sialic acid surface coat.