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Optic nerve microvessels: a partial molecular definition of cell surface anionic sites
J G Lawrenson1, A R Reid, M N Ghabriel
1Reta Lila Weston Institute of Neurological Studies, University College London Medical School, U.K.
Experimental Eye Research
|October 1, 1995
Summary
Anionic sites on optic nerve endothelial cells are primarily sialoglycoproteins. These sites, crucial for blood interactions and permeability, were characterized using electron microscopy and enzyme digestion, revealing their molecular composition.
Area of Science:
- Vascular Biology
- Cell Biology
- Neuroscience
Background:
- Endothelial cells (EC) possess negatively charged microdomains (anionic sites) in their glycocalyx.
- These anionic sites are vital for interactions with blood components and regulate vascular permeability.
- The composition of these sites varies anatomically, but they remain uncharacterized in optic nerve EC.
Purpose of the Study:
- To characterize the molecular composition of luminal anionic sites on optic nerve endothelial cells.
- To investigate the role of specific molecular components in forming these anionic sites.
Main Methods:
- Optic nerves from Sprague-Dawley rats were isolated and fixed.
- Anionic sites were labeled using cationic colloidal gold (CCG) and cationic ferritin (CF) with electron microscopy.
- Enzyme digestion (heparitinase, trypsin, proteinase K, papain, neuraminidase) and lectin labeling (WGA) were used to probe molecular composition.
Main Results:
- Uniform CCG and CF labeling was observed on the luminal EC surface, exceeding abluminal labeling.
- Enzyme digestion revealed that proteolytic and glycolytic enzymes significantly reduced CCG binding.
- Neuraminidase almost completely eliminated labeling, indicating the primary role of sialic acid residues.
Conclusions:
- Luminal EC anionic sites in the optic nerve are predominantly composed of sialoglycoproteins.
- Wheat germ agglutinin (WGA) binding suggests a significant contribution of N-acetylneuraminic acid residues.