LOCALIZATION OF ACID MUCOPOLYSACCHARIDES AND SIALIC ACID CONTAINING GLYCOPROTEINS IN RENAL CORTEX AND INNER MEDULLA BY A COMBINED ELECTRON MICROSCOPIC HISTOCHEMICAL METHOD

Acid mucopolysaccharides and sialic acid containing glycoproteins are localized in the kidney by the colloidal iron method. All cell membranes in cortex and medulla are coated by positive colloidal iron particles. This iron-coat variies in thickness at different cells and at the luminal, lateral and basal surface of one cell, too. Tubules and capillaries show a parallelism between the thickness of the outer leaflet of the plasmalemm unit-membrane and the thickness of the colloidal iron coat. Biochemical analyses of cell membranes and the negative result of the colloidal iron reaction after sialidase-treatment allow to conclude, that this colloidal iron coat represents sialic acid containing glycoproteins. This glycoprotein-coat is part of the whole cell membrane. In some cells the endoplasmatic reticulum reacts with colloidal iron. Here, too, sialic acid was found by biochemical analysis. The positive colloidal iron reaction in the extracellular space depends on acid mucopolysaccharides and sialic acid. In the lamina rara interna and externa of the glomerular basement membrane the positive colloidal iron reaction correlates to the sialic acid content. © 1969 Springer-Verlag.