An increased calcium accumulation in ATP-depleted red cells of the patients with paroxysmal nocturnal hemoglobinuria.

A marked increase in calcium (Ca) uptake (85.5 +/- 39.0 nmoles/ml RBC/2 hr) was observed in ATP-depleted red cells of patients with paroxysmal nocturnal hemoglobinuria (PNH) as compared to ATP-depleted normal red cells (8.0 +/- 2.0). The extent of increased Ca uptake in the PNH red cells was related to the extent of increased sensitivity to complement, as judged by the sugar water test (p less than 0.001) and the acidified serum test (p less than 0.001), and inversely correlated to the decreased activity of red cell acetylcholinesterase (p less than 0.01). The results may indicate that increased calcium uptake in PNH red cells is a possible intrinsic defect of the red cell membranes in the disorder.