Quantitative distribution of glycosaminoglycans in young and senile (cataractous) anterior lens capsules

The ocular lens is surrounded by the lens capsule, which is an elastic and unusually thick basal membrane. Anionic sites are thought to be responsible for charge-selective permeability barriers in basal membranes. We have used cationic colloidal gold as a tracer for anionic binding sites to investigate the distribution of glycosaminoglycans in young and senile (cataractous) lens capsules. Using electron microscopy, combined with the cationic colloidal gold post-embedding technique, glycosaminoglycans were localized distinctively in a continuous layer immediately apposed to the lens epithelium, which has been referred to as the lamina lucida. The amount of gold particles decreased from the internal (lenticular) side of the capsule, toward the center, followed by an increase of label intensity toward the external (humoral) side. The humoral surface is characterized by a highly anionic layer measuring 1.5--4 micro m. Immunofluorescence microscopy localized three main types of glycosaminoglycans (heparan-, chondroitin- and dermatan sulfate) within this distinctive layer. Quantitative electron microscopy demonstrated reduced amounts of glycosaminoglycans at the lenticular and humoral side of senile (cataractous) lens capsules. The distinctive spatial distribution of glycosaminoglycans in human lens capsules is discussed in terms of age-related structural and functional changes.