Erythrocyte membrane ATPase activity of G6PD-deficient individuals and the effect of primaquine metabolite(s) on membrane ATPase enzymes.

Erythrocyte membrane Na+/K+, Ca2+/Mg2+ and Mg2+ ATPase activities in addition to the calmodulin-activated Ca2+/Mg2+ ATPase enzyme were measured in both G6PD-deficient and normal individuals. Although all three membrane ATPase activities were somewhat higher in the G6PD-deficient erythrocytes, only activated Ca2+/Mg2+ ATPase activity was significantly increased. The effect of primaquine on the membrane ATPases was also compared with other ATPase inhibitors. Primaquine was ineffective on erythrocyte membrane ATPase in-vitro. However, sera containing primaquine metabolite(s) were inhibitory to Ca2+/Mg2+ and Mg2+ ATPase systems of only G6PD-deficient erythrocytes. Other ATPase inhibitors showed a similar inhibitory effect in G6PD-deficient and normal erythrocytes, indicating a specific influence of primaquine on ATPase system in G6PD deficiency. It is suggested that this effect of primaquine may be an additional factor for haemolysis observed in the people with GdB- type of G6PD deficiency among the Mediterranean populations.