Acidic calcium pools in intraerythrocytic malaria parasites.
Calcium uptake by permeabilized P. chabaudi malaria parasites was measured at the trophozoite stage to assess calcium accumulation by the parasite organelles. As determined with 45Ca2+, the total calcium in the parasite was found to be 11 pmoles/10(7) cells. When the K+/H+ uncoupling agent, nigericin was present, this level fell to 6.5 pmoles/10(7) cells. A similar regulatory mechanism operates in P. falciparum, since addition of nigericin to intact parasites in calcium free-medium resulted in a transient elevation of free calcium in the parasite cytosol, as judged by fluorescent imaging of single cells loaded with the calcium indicator fluo-3,AM. 7-Chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl) and monensin, inhibitors of H+ ATPases and K+/H+ ionophore respectively, induced calcium elevation in fluo-3, AM-labeled intact P. chabaudi parasites. We conclude that malaria parasites utilize acidic intracellular compartments to regulate their cytosolic free calcium concentration.
Universidade de São Paulo, Instituto de Biociências, Departamento de Fisiologia, Brazil.
C R
CR
Garcia
S E
SE
Ann
E S
ES
Tavares
A R
AR
Dluzewski
W T
WT
Mason
F B
FB
Paiva
D009327:4-Chloro-7-nitrobenzofurazan / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000814:Aniline Compounds; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D004912:Erythrocytes / Q000469:parasitology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D051379:Mice; D018715:Microscopy, Video; D008985:Monensin / Q000494:pharmacology; D009550:Nigericin / Q000494:pharmacology; D010539:Permeability; D016788:Plasmodium chabaudi / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D054328:Proton Pump Inhibitors; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D013050:Spectrometry, Fluorescence; D014617:Vacuoles / Q000378:metabolism*; D014966:Xanthenes
D000814:Aniline Compounds; D054328:Proton Pump Inhibitors; D014966:Xanthenes; C059715:Fluo-3; D000255:Adenosine Triphosphate; D008985:Monensin; D006180:Proton-Translocating ATPases; D009327:4-Chloro-7-nitrobenzofurazan; D009550:Nigericin; D002118:Calcium