Ultrastructural demonstration of proteoglycans in adult rat cornea.

Proteoglycans in the adult rat cornea were demonstrated at the electron microscope level using two approaches: (a) staining with cuprolinic blue dye in the presence of 0.3 MgCl2, and (b) immunocytochemical localization of glycosaminoglycans with monoclonal antibodies and protein A-gold complexes. In the stroma two kinds of cuprolinic blue-induced filaments were morphologically differentiated and characterized according to their sensitivity to enzymatic degradations as keratan sulphate-rich and chondroitin-dermatan sulphate-rich proteoglycans respectively. Both types were mostly associated with collagen fibres, occupying the whole stroma except in certain areas whose significance is discussed. By immunocytochemistry, anterior and posterior regions of the stroma were found to be richer in chondroitin sulphate than the middle part, whereas keratan sulphate showed an homogeneous distribution throughout the stroma. Glycosaminoglycans were also detected in corneal basement membranes, epithelium and endothelium. The latter localizations are discussed in the light of what is known at present about the production of glycosaminoglycans by corneal cells.