title: Calcium transport of Plasmodium chabaudi-infected erythrocytes.
abstract: The calcium content and transport processes of Plasmodium chabaudi-infected rat erythrocytes were analyzed by atomic absorption spectroscopy and 45Ca2+ flux measurements. Infected erythrocytes, after fractionation on metrizamide gradients according to stage of parasite development, exhibited progressively increasing levels of Ca2+ with schizont and gametocytes containing 10- to 20-fold greater calcium levels than normal cells (0.54 +/- 0.25 nmol/10(8) cells). 45Ca2+ flux experiments showed both increased influx and decreased efflux in infected erythrocytes. Tris/NH4Cl lysis of normal erythrocytes preloaded with 45Ca2+ with the Ca2+ ionophore A23187 released less than 90% of cell calcium after incubation in ethyleneglycol bis(aminoethylether) N,N'-tetraacetic acid containing buffer, whereas lysis of the infected erythrocyte membrane resulted in release of 10-20% cell Ca2+, with the remaining portion associated with the isolated parasite fraction. This information together with the effects of various metabolic inhibitors indicates the presence of a parasite Ca2+ compartment in P. chabaudi-infected erythrocytes. Dicyclohexylcarbodiimide (DCCD) an inhibitor of proton ATPases of chloroplasts, bacteria, yeast, and mitochondria, and the proton ionophore, carbonyl cyanide m-chlorophenylhydrazone (CCCP), inhibited Ca2+ influx and stimulated efflux from infected cells. These results combined with evidence for a DCCD- and CCCP-sensitive membrane potential in P. chabaudi-infected cells (Mikkelsen et al., accompanying manuscript) suggest that Ca2+ transport of intraerythrocytic parasites is coupled to a proton-motive force across the Plasmodia plasma membrane.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism* / Q000469:parasitology; D006859:Hydrogen / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D008288:Malaria / Q000097:blood*; D008297:Male; D010961:Plasmodium / Q000187:drug effects; D051381:Rats
chemical_list: D007473:Ion Channels; D000001:Calcimycin; D004024:Dicyclohexylcarbodiimide; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006859:Hydrogen; D004492:Edetic Acid; D002118:Calcium