TY - JOUR
T1 - The New Permeability Pathways Induced by the Malaria Parasite in the Membrane of the Infected Erythrocyte
T2 - Comparison of Results Using Different Experimental Techniques
AU - Ginsburg, H.
AU - Stein, W. D.
PY - 2004/3/15
Y1 - 2004/3/15
N2 - The membrane of erythrocytes infected with malaria parasites is highly permeable to a large variety of solutes, including anions, carbohydrates, amino acids, nucleosides, organic and inorganic cations and small peptides. The altered permeability is presumed to be due to the activation of endogenous dormant channels, the new permeability pathways. The latter have been studied by different techniques - isosmotic lysis and tracer fluxes - and recently by patch-clamping. Here we analyze all available published data and we show that there is generally a good agreement between the two first methods. From the fluxes we calculate the number of channels per cell using reasonable assumptions as to the radius of the channel, and assuming that penetration through the channel is by diffusion through a water-filled space. The number of channels so calculated is <10 for most solutes, but ∼400 for anions and the nucleosides thymidine and adenosine. This latter number is not far from that calculated from patch-clamp experiments. However, the anion flux measured directly by tracer is an order of magnitude larger than expected from conductance measurements. We conclude that the new permeability pathways consist of two types of channels; one is present in small number, and is charge- and size-selective. The other type is about 100-fold more abundant and is anion-selective, but does not admit non-electrolytes other than perhaps nucleosides.
AB - The membrane of erythrocytes infected with malaria parasites is highly permeable to a large variety of solutes, including anions, carbohydrates, amino acids, nucleosides, organic and inorganic cations and small peptides. The altered permeability is presumed to be due to the activation of endogenous dormant channels, the new permeability pathways. The latter have been studied by different techniques - isosmotic lysis and tracer fluxes - and recently by patch-clamping. Here we analyze all available published data and we show that there is generally a good agreement between the two first methods. From the fluxes we calculate the number of channels per cell using reasonable assumptions as to the radius of the channel, and assuming that penetration through the channel is by diffusion through a water-filled space. The number of channels so calculated is <10 for most solutes, but ∼400 for anions and the nucleosides thymidine and adenosine. This latter number is not far from that calculated from patch-clamp experiments. However, the anion flux measured directly by tracer is an order of magnitude larger than expected from conductance measurements. We conclude that the new permeability pathways consist of two types of channels; one is present in small number, and is charge- and size-selective. The other type is about 100-fold more abundant and is anion-selective, but does not admit non-electrolytes other than perhaps nucleosides.
KW - Anion channel
KW - Comparative analysis
KW - Infected erythrocyte
KW - Malaria
KW - Membrane permeability
KW - Plasmodium falciparum
UR - http://www.scopus.com/inward/record.url?scp=1442359893&partnerID=8YFLogxK
U2 - 10.1007/s00232-003-0646-7
DO - 10.1007/s00232-003-0646-7
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C2 - 15014913
AN - SCOPUS:1442359893
SN - 0022-2631
VL - 197
SP - 113
EP - 122
JO - Journal of Membrane Biology
JF - Journal of Membrane Biology
IS - 2
ER -