Lipopolysaccharide treatment modifies pH- and cation-dependent ecto-ATPaseactivity of endothelial cells

The aim of this study was to investigate the distribution pattern of Ca2+- and Mg2+-dependent ecto-ATPases on the surface of rat brain capillary endot helial cells (ECs) in control and lipopolysaccharide (LPS)-treated animals. Ecto-ATPases in the membrane of vascular endothelial cells are suggested t o play a crucial role in thromboregulation. Loss of this enzyme activity af ter oxidative stress and upregulation of the enzyme chain hydrolyzing extra cellular ATP after transient forebrain ischemia have also been reported. We used histochemistry to localize the activities of this enzyme on ECs and f ound pH- and cation-dependent changes in the localization of enzyme activit y both in control and in LPS-treated animals. These findings suggest the pr esence of more than one ecto-ATPase enzyme on the surface of rat capillary ECs. The different behavior of ECs after LPS treatment is the target of fur ther investigations. The increased ecto-nucleotidase activity might play a role in nucleotide-mediated cellular responses after bacterial infections.