Hemolysis of PNH erythrocytes in isotonic solutions of choline esters

¹ Hematology Service, Department of Medicine, Vanderbilt University School of Medicine and Hospital, Nashville, Tennessee

When the acetylcholinesterase activity of normal cells suspended in isotonic choline ester solutions is inhibited by the addition of physostigmine, these cells are more sensitive to H⁺ ions (i.e. hemolyze at a relatively higher pH) than the control cells. Such observations have led to the hypothesis that acetylcholinesterase may control membrane pH. Erythrocytes of paroxysmal nocturnal hemoglobinuria (PNH) have been demonstrated to be markedly deficient in acetylcholinesterase activity. PNH cells were incubated in isotonic solutions of choline esters and hemolysis and pH changes were followed with time. Such enzyme-deficient cells did not hemolyze at a relatively higher pH, as reported in the case of physostigmine-treated normal cells. The results of these experiments provide no concrete evidence that the erythrocyte acetylcholinesterase enzyme plays any role as an enzyme buffer system. As yet, no simple explanation has been found to correlate the acetylcholinesterase deficiency of PNH erythrocytes with their known susceptibility to hemolysis in acidified serum.

Note:
(With the Technical Assistance of Dorris E. Webb)