Platelet aggregation and the ouabain-insensitive ATPase. Ecto-ATPase, reflection of membrane integrity

The ecto-ATPase activity of washed human platelets has been characterized by a higher-performance liquid chromatographic method. Mg++ was found to stimulate ecto-ATPase activity more strongly than Ca++. The combination of Mg++ and Ca++ at increasing concentrations caused diminishing activity levels. Elevated ecto-ATPase activity was also found in platelets incubated with prostaglandin E1 (PGE1) or potassium cyanide (KCN). It is proposed that the increase of ecto-ATPase activity is related to the extrusion or exposure of plasma membrane containing a ouabain-insensitive ATPase. The role of ecto-ATPase in platelet aggregation is discussed in light of these findings.