DISTRIBUTION AND ANALYSIS OF SURFACE-CHARGE ON BRAIN ENDOTHELIUM IN-VITRO AND IN-SITU

Vascular endothelial cells are associated with a number of anionic mol ecules. These anions are important in endothelial function, particular ly in regulating permeability, haemostasis and cellular traffic. To ex plore the nature and distribution of anions on the brain endothelial c ell (BEC) surface, we have examined rat brain endothelium in culture, and in situ. The anionic sites were probed with cationic colloidal gol d and cationised ferritin, and visualised by light microscopy. Additio nally we compared the distribution of the anionic sites on BEC with th at present on other endothelial cell types in culture. The predominant anion detected on BEC was heparan sulphate (HS). This was distributed throughout the cell membrane, but was most densely associated with in tercellular junctions. This pattern was distinct from the anionic loca tions observed in endothelia from aorta and epididymal fat microvessel s. The distribution of anions was dependent on the age of cultured cel ls, with only minimal levels of HS seen at the periphery of younger ce lls. The nature and distribution of negative charge was different in s itu. Here, sialic acid was the major surface anion, with only a small contribution from HS. The significance of these findings are discussed in relation to endothelial function in normal tissue and in pathologi cal conditions.