Immunogold localization of basal laminar heparan sulfate proteoglycan in rat brain and retinal capillaries.

Heparan sulfate proteoglycan was localized in the basal lamina of the brain and retinal capillaries, using an antibody to the core protein of the proteoglycan and a postembedding immunogold labeling method at the ultrastructural level. Gold particles appeared to be randomly distributed in the basal lamina of both types of capillaries, in contrast to discrete ruthenium red-staining sites near the endothelial plasma membrane, as shown in previous studies of the retinal vessel. The present study not only agrees with previous biochemical and immunofluorescence studies, but also provides a more precise localization of the antigen. Furthermore, the method can be useful for quantitative studies.