The ultrastructural basis of permeability to proteins in normal and nephrotic glomeruli. Electron microscopic and micropuncture studies using ferritin as a tracer.

Following microinjection of ferritin into urinary space of the rat renal glomerulus in vivo, permeability of the visceral epithelial wall was examined with electron microscope. Results indicated that in normal glomeruli ferritin molecules can be retained by the slit diaphragmata of the eithelial cells; this suggests a barrier function of the slit diaphragmata. The nephrotic glomeruli, observations suggested a channel-like pathway to proteins penetrating the epithelial layer. The channel is formed by only one single cell and therefore, the term 'percellular channel' is proposed for that formation.