Electrophysiological properties of the plasmodium falciparum-induced cation conductance of human erythrocytes

Intraerythrocyte survival of the malaria pathogen Plasmodium falciparum depends on the induction of the new-permeability-pathways (NPPs) in the host cell membrane. NPPs are characterized as anion- and organic osmolyte-permeable channels which also exhibit a low but significant permeability for inorganic cations. To disclose the electrophyiologial properties of this infection-induced cation permeability whole-cell currents were recorded in Plasmodium falciparum-infected human erythrocytes (pRBC) using bath and pipette solutions with low Cl- concentrations. The data disclose a nonselective cation conductance (G(cat)) which activated upon removal of extracellular Cl-. Upon activation, G(cat) was 0.3 +/- 0.05 nS (n=16) in control RBC and 2.0 +/- 0.3 nS (n = 32) in pRBC indicating an induction of G(cat) during the infection. G(cat) of pRBC a exibited a relative permselectivity for monovalent cations of Cs(+)similar toK+>Na+>Li+ (P-Na/P-K similar to 0.5) with a significant permeability for Ca2+. G(cat) of pRBC was inhibited by NPPs blockers (furosemide and NPPB) and cation channel blockers (amiloride, EIPA, GdCl3) with the highest sensitivity to EIPA (IC(50)similar to0.5muM). Most importantly, the blocker sensitivities differed between the infection-induced anion conductances and G(cat) suggesting that G(cat) and the anion conductances represent different channel proteins which in concert build up the NPPs. Copyright (C) 2003 S. Karger AG, Basel.