Characteristics of Ca2+ transport by Trypanosoma cruzi mitochondria in situ.
The use of digitonin to permeabilize Trypanosoma cruzi plasma membrane has allowed the study of Ca2+ transport and oxidative phosphorylation in mitochondria in situ (R. Docampo and A. E. Vercesi (1989) J. Biol. Chem. 264, 108-111). The present results show that these mitochondria are able to build up and retain a membrane potential as indicated by a tetraphenylphosphonium-sensitive electrode. Ca2+ uptake caused membrane depolarization compatible with the existence of an electrogenically mediated Ca2+ transport mechanism in these mitochondria. Addition of Ca2+ or ethylene glycol bis (beta-aminoethyl ether) N-N'-tetraacetic acid to these preparations under steady-state conditions was followed by Ca2+ uptake or release, respectively, tending to restore the original Ca2+ "set point" at about 0.9 microM. In addition, large amounts of Ca2+ were retained by T. cruzi mitochondria even after addition of thiols and NAD(P)H oxidants such as t-butyl hydroperoxide, diamide, and the 1,2-naphthoquinone beta-lapachone. However, when ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine in the presence of antimycin A was used as subtrate, beta-lapachone caused pyridine nucleotide oxidation, and Ca2+ accumulation by these mitochondria was considerably lower than in control preparations, this effect being dose-dependent.
Docampo
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Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, Brazil.
Vercesi
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AE
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004072:Digitonin / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009285:Naphthoquinones / Q000494:pharmacology; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D010084:Oxidation-Reduction; D010545:Peroxides / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D011919:Rats, Inbred Strains; D014349:Trypanosoma cruzi / Q000648:ultrastructure*; D020122:tert-Butylhydroperoxide
D009285:Naphthoquinones; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D010545:Peroxides; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D004533:Egtazic Acid; D009249:NADP; D000244:Adenosine Diphosphate; C014638:beta-lapachone; D020122:tert-Butylhydroperoxide; D004072:Digitonin; D002118:Calcium; C013289:tetraphenylphosphonium