Figure 1. Effect of the oxidising agent H₂O₂ on pH_i in isolated parasites.

(A) Effect of H₂O₂ (2 mM) and the V-type H⁺ ATPase inhibitor concanamycin A (75 nM) on pH_i. The reagents were added at the point indicated by the white triangle. The traces shown are from a single experiment on a suspension of isolated BCECF-loaded 3D7 P. falciparum trophozoites (5×10⁷ cells/ml) at 37°C and are representative of those obtained in five similar experiments. (B) Effect of parasite concentration on the response of pH_i to the oxidising agent H₂O₂ (4 mM, added at the point indicated by the white triangle) in suspensions of isolated BCECF-loaded 3D7 parasites at 37°C. ΔpH_i indicates the deviation from the initial resting pH_i. The traces shown are from a single experiment but are representative of those obtained in three similar experiments. (C) Effect of H₂O₂ (2 mM, added at the point indicated by the white triangle) on pH_i in single isolated SNARF-loaded D10 parasites immobilized on polylysine coated coverslips at 22°C. The data showing cytosolic pH_i are averaged from 79 individual cells carried out on three different days, and are shown±S.D.