CYTOCHEMICAL STUDY OF THE EFFECT OF ALUMINUM CULTURED BRAIN MICROVASCULAR ENDOTHELIAL-CELLS

The cytotoxic effect of aluminium was studied on cultured goat brain m icrovascular endothelial cells used as an in vitro model of the blood- brain barrier. Confluent monolayers of these cells were exposed for 4 days to aluminium maltol and, for control purposes, to maltol alone, a nd also to cadmium chloride as a known cytotoxic substance. The locali zation of plasmalemma-bound enzymatic activities of 5'-nucleotidase an d Ca2+-ATPase and the distribution of sialic acid residues were studie d at the ultrastructural level. It was observed that the reaction for 5'-nucleotidase activity was only insignificantly affected, indicating its resistance to the cytotoxic action of both substances used. On th e contrary, the activity of Ca2+-ATPase was evidently suppressed, espe cially in the interendothelial clefts where junctional complexes are p resumably to be formed. Aluminium also affects the density of sialic a cid residues, as shown by their redistribution, leading to the appeara nce of relatively long segments of unlabelled apical cell surface. The data obtained suggest that observed changes in the localization of Ca 2+-ATPase and sialic acid residues can lead ultimately to impairment o f the formation and maintenance of intercellular junctions and to dist urbances in the negatively charged domains of the endothelial cell sur face. Whether these alterations, induced in vitro, contribute to in vi vo disturbances of blood-brain barrier function requires further exper imental study.