TY - JOUR
T1 - Novel anion dependence of induced cation transport in malaria-infected erythrocytes
AU - Kirk, Kiaran
AU - Horner, Heather A.
PY - 1995/10/13
Y1 - 1995/10/13
N2 - Following invasion by the malaria parasite there appear in the parasitized erythrocyte new ('induced') permeation pathways that mediate the transport of a wide variety of small solutes. Although anion-selective, these pathways have a significant cation permeability and cause a substantial increase in the basal leak of cations into and out of the infected cell. In this study of human erythrocytes infected in vitro with Plasmodium falciparum it was shown that the transport of monovalent cations (Rb+ and choline), but not that of a nonelectrolyte (sorbitol) or a monovalent anion (lactate), via the malaria- induced pathways is strongly dependent on the nature of the anion in the suspending medium. Substitution of NO3/- for Cl- resulted in a 4-6-fold increase in the unidirectional influx and efflux of Rb+, and a 2-3-fold increase in the influx of choline via the induced pathways. By contrast, replacement of Cl- with NO3/- caused a slight (although not significant) decrease in the malaria-induced influx of sorbitol and lactate. Hemolysis experiments with a range of K+ salts revealed that the net influx of K+ into infected cells showed the same novel anion dependence as seen for the unidirectional flux of Rb+ and choline, with hemolysis occurring much faster in iso-osmotic KNO3 and KSCN solutions than in KCl, KBr, or KI solutions. Hemolysis in the corresponding Na+ salt solutions was very much slower, consistent with the induced pathways being selective for K+ over Na+, and raising the possibility that the efflux of cell K+ via these pathways may play a role in host cell volume regulation. A number of models that would account for the anion dependence of malaria-induced cation transport are considered.
AB - Following invasion by the malaria parasite there appear in the parasitized erythrocyte new ('induced') permeation pathways that mediate the transport of a wide variety of small solutes. Although anion-selective, these pathways have a significant cation permeability and cause a substantial increase in the basal leak of cations into and out of the infected cell. In this study of human erythrocytes infected in vitro with Plasmodium falciparum it was shown that the transport of monovalent cations (Rb+ and choline), but not that of a nonelectrolyte (sorbitol) or a monovalent anion (lactate), via the malaria- induced pathways is strongly dependent on the nature of the anion in the suspending medium. Substitution of NO3/- for Cl- resulted in a 4-6-fold increase in the unidirectional influx and efflux of Rb+, and a 2-3-fold increase in the influx of choline via the induced pathways. By contrast, replacement of Cl- with NO3/- caused a slight (although not significant) decrease in the malaria-induced influx of sorbitol and lactate. Hemolysis experiments with a range of K+ salts revealed that the net influx of K+ into infected cells showed the same novel anion dependence as seen for the unidirectional flux of Rb+ and choline, with hemolysis occurring much faster in iso-osmotic KNO3 and KSCN solutions than in KCl, KBr, or KI solutions. Hemolysis in the corresponding Na+ salt solutions was very much slower, consistent with the induced pathways being selective for K+ over Na+, and raising the possibility that the efflux of cell K+ via these pathways may play a role in host cell volume regulation. A number of models that would account for the anion dependence of malaria-induced cation transport are considered.
UR - http://www.scopus.com/inward/record.url?scp=0028884242&partnerID=8YFLogxK
U2 - 10.1074/jbc.270.41.24270
DO - 10.1074/jbc.270.41.24270
M3 - Article
C2 - 7592635
AN - SCOPUS:0028884242
SN - 0021-9258
VL - 270
SP - 24270
EP - 24275
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 41
ER -