Figure 3.

Response of Saponin-Isolated P. falciparum Trophozoites to an Imposed Intracellular Na⁺ Load

(A) Trace showing the effect of removal of extracellular K⁺ on [Na⁺]_i in SBFI-loaded parasites. At the time point indicated by the open triangle, the cells (in standard saline) were washed twice by centrifugation and resuspension in a K⁺-free saline (in which K⁺ was replaced isosmotically with Na⁺). At the time point indicated by the closed triangle, 10 mM K⁺ (as KCl) was added to the suspension. The trace is representative of that obtained from at least twenty independent cell preparations.

(B) Trace showing the effect of the same maneuvers (i.e., removal of extracellular K⁺ at the point indicated by the open triangle then restoration at the point indicated by the closed triangle) on the pH_i in BCECF-loaded parasite suspension. The trace is representative of that obtained from at least seven independent cell preparations.

(C–E) Effect of ion transport inhibitors on the recovery of [Na⁺]_i from an imposed intracellular Na⁺ load. SBFI-loaded parasite suspensions were subjected to a Na⁺ load (by suspension in K⁺-free medium) as illustrated in (A), and the traces commenced with the addition to the suspension of 10 mM KCl either with (gray traces) or without (control, black traces) (C) EIPA (20 μM), (D) furosemide (100 μM), or (E) NITD246 (1 nM or 5 nM). The traces shown are each representative of those obtained from at least three independent cell preparations.