[Ecto-ATPases in leukocytes and its modification by drugs]

The ecto-ATPase is located on the external surface of the plasma membrane of intact cells. The enzyme splits exogeneous ATP in the presence of Mg2+ into ADP and inorganic phosphate. This enzyme has been found on a variety of cells of various species in different activities. In leukocytes sulfhydryl groups are essential for the structure and function of the ecto-ATPase. The physiological and biochemical significance of the ecto-ATPase for cells remains unclear. Drugs may influence ecto-ATPase activity and simultaneously various cell functions. Tricyclic antidepressants and phenothiazine tranquilizers in micromolar concentrations inhibit the ecto-ATPase in granulocytes and reduce the phagocytic activity of the cells. The inhibition of the ecto-ATPase of rat thymocytes by organic tin compounds is not connected with a reduced spontaneous migration of the cells in vitro. Newer results indicate, that the ecto-ATPase activity of thymocytes and other cells is changing during maturation and differentiation.