Adenosine Triphosphatase Activity of the Red Cell Membrane in Paroxysmal Nocturnal Haemoglobinuria

Abstract

Summary: The activity of the ATPase complex of red cell ghosts as well as the activity of the ATPase components, Mg2+ ATPase and Mg2+, Na+ and K+ ‐dependent ATPase was studied in patients with paroxysmal nocturnal haemoglobinuria (PNH). In ghosts prepared by osmotic haemolysis a significantly higher ATPase activity was found in PNH cells than in normal red cells. Ghosts exposed to the effect of saponin showed a significant increase of ATPase activity both in normal and PNH red cells; however, the increase of activity was markedly higher in PNH ghosts than in ghosts of normal red cells. Both Mg2+‐dependent and Mg2+, Na+ and K+‐dependent ATPase contribute to this increase. The protein content in osmotic ghosts of PNH red cells was higher than normal; but after treating these ghosts with saponin, no marked difference in protein content was found. By comparison with the results of ATPase activity obtained using red cells from non‐splenectomized individuals with hereditary spherocytosis with similar reticulocyte values it is assumed that the increase of ATPase activity is not due to younger cells in the blood but is a further manifestation of the abnormality of the cell membrane in PNH. ATPase activity is present mostly in the inactive form in the red cell membrane and is activated (unmasked) by structural damage of the cell membrane. It is suggested that the increased ATPase activity in the PNH red cell membrane represents a manifestation of abnormal structural arrangement which is more susceptible to damage. The deviations found in the content and metabolism of organic phosphates are probably caused by the younger population of red cells in PNH.