ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
Intraerythrocytic malaria parasites produce vast amounts of lactic acid through glycolysis. While the egress of lactate is very rapid, the mode of extrusion of H+ is not known. The possible involvement of a Na+/H+ antiport in the extrusion of protons across the plasma membrane of Plasmodium falciparum has been investigated by using the fluorescent pH probe 6-carboxyfluorescein. The resting cytosolic pH was 7.27 ± 0.1 in ring stage parasites and 7.31 ± 0.12 in trophozoites. Spontaneous acidification of parasite cytosol was observed in Na+-medium and realkalinization occurred upon addition of Na+ to the medium in a concentration-dependent manner, with no apparent saturation. The rate of H+-at the ring stage was higher than that at the trophozoite stage due to the larger surface/volume ratio of the young parasite stage. Na+-H+-was: 1) inhibited by the Na+/H+ inhibitors amiloride and 5-(N-ethyl-isopropyl) amiloride (EIPA), though at relatively high concentrations; 2) augmented with rising pH6 (pHi = 6.2 [Na+]o = 30 mM); and 3) decreased with increasing pHi (pHo = 7.4; [Na+]o = 30 mM). The pHi and the pHo dependencies of H+-were almost identical at all parasite stages. Only at pHi 〉 7.6 efflux was totally obliterated. The target of this inhibitory effect is probably other than the antiport. Results indicate that H+-is mediated by a Na+/H+ antiport which is regulated by host and parasite pH and by the host cytosol sodium concentration. The proton transport capacity of the antiport can easily cope with all the protons of lactic acid produced by parasite's glycolysis. © 1993 Wiley-Liss, Inc.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1041540311
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