1988 Volume 30 Issue 1 Pages 33-47
In phylogenetically and ontogenetically immature glomerulus of chicken embryo mesonephros, development of the glomerular capillary wall forming filtration barrier was observed with an electron microscope and the factors participating in its selective permeability were studied. In addition, in each developmental stage of primitive glomerular basement membrane (PGBM) of the mesonephros, the permeability of PGBM was studied with anionic ferritin and anionic site of PGBM were observed with cationized ferritin and polyethyleneimine. Simultaneously, participation of the size selective barrier and charge selective barrier in PGBM was studied and the following conclusion was obtained. (1) The PGBM of the mesonephros consisted mainly of epithelial basement membrane. With development of the glomerulus, PGBM of the mesonephros increased its thickness and became electron dense. Study on permeability for anionic ferritin revealed only extremely rough formation of the size selective barrier in PGBM. (2) Similarly to the metanephros of the higher mammals, anionic sites were ovserved in the lamina rarae of PGBM in the mesonephros at the early stage of glomerular development. However, in this experiment, it was not clear whether the anionic substance forms the charge selective barrier or not. (3) The endothelial fenestrae and their diaphragm and epithelial slit pore were confirmed to make morphological change similar to that in mammals metanephros. I was suggested that endothelial fenestrae and their diaphragm might play an important role as filtration barrier in PGBM of the mesonephros with immature size and charge selective barriers.
