APPLICATION OF CATIONIC COLLOIDAL GOLD STAINING FOR THE DEMONSTRATIONOF ANIONIC SITES

Positively charged colloidal gold (cationic colloidal gold) stains neg atively charged areas (anionic sites) on histological sections. Specim ens embedded in hydrophilic resins are especially suitable for the pre cise localization of anionic sites with cationic gold in post-embeddin g method. Enzyme digestion on the sections embedded in hydrophilic res ins before the staining with cationic gold enabled us to identify the molecules such as sialic acid, chondroitin sulfate, and heparan sulfat e which cause anionic charge. Studies using cationic colloidal gold ha ve been published from various fields of biology and medicine. In the kidney, glomerular basement membranes and glycocalyx of epithelial cel ls show anionic sites and these negative charges are thought to play i mportant roles in the selective permeability in the glomerulus. Distri butions of anionic sites in the glomerular basement membranes and epit helial cells are altered in diseases and in experimentally induced nep hropathy. My laboratory has studied the distribution and enzyme suscep tibility of anionic sites in human sweat glands, epidermis, and skin t umors. Cationic gold stains eccrine and apocrine sweat glands in a dif ferent manner. This would be helpful for an accurate diagnosis of swea t gland tumors. Data so far obtained suggest cationic colloidal gold i s a useful tool to study structures and functions of cells and tissues with histochemical methods.