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 use d cationic colloidal gold as a tracer for anionic binding sites to investig ate the distribution of glycosaminoglycans in young and senile (cataractous ) lens capsules. Using electron microscopy, combined with the cationic coll oidal gold post-embedding technique, glycosaminoglycans were localized dist inctively in a continuous layer immediately apposed to the lens epithelium. which has been referred to as the lamina lucida. The amount of gold partic les decreased from the internal (lenticular) side of the capsule, toward th e center, followed by an increase of label intensity toward the external (h umoral) side. The humoral surface is characterized by a highly anionic laye r measuring 1.5-4 mum. Immunofluorescence microscopy localized three main t ypes of glycosaminoglycans (heparan-, chondroitin- and dermatan sulfate) wi thin 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 o f glycosaminoglycans in human lens capsules is discussed in terms of age-re lated structural and functional changes. (C) 2001 Academic Press.