Ca2+ transport in digitonin-permeabilized trypanosomatids.
The use of digitonin to permeabilize Leishmania mexicana mexicana, Leishmania agamae, and Crithidia fasciculata plasma membranes enabled us to study Ca2+ transport in situ. The present results show that the mitochondria of these trypanosomatids 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. Ca2+ uptake was partially inhibited by ruthenium red, almost totally inhibited by carbonyl cyanide p-trifluoromethoxyphenylhydrazone, and stimulated by inorganic phosphate. Large amounts of Ca2+ were retained by C. fasciculata mitochondria even after addition of thiols and NAD(P)H oxidants such as t-butylhydroperoxide and diamide. In contrast, Ca2+ was not retained in the matrix of Leishmania sp. mitochondria for long periods of time. In addition to the mitochondrial Ca2+ uptake, a vanadate-sensitive Ca2(+)-transporting system was also detectable in these trypanosomatids.
Vercesi
A E
AE
Departamento de Bioquimica, Instituto de Biologia, UNICAMP, Campinas, S.P., Brazil.
Macedo
D V
DV
Lima
S A
SA
Gadelha
F R
FR
Docampo
R
R
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D003421:Crithidia / Q000187:drug effects / Q000378:metabolism; D004072:Digitonin / Q000494:pharmacology*; D007894:Leishmania mexicana / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009861:Onium Compounds / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000494:pharmacology; D014345:Trypanosoma / Q000187:drug effects / Q000378:metabolism*
D009861:Onium Compounds; D009943:Organophosphorus Compounds; D004072:Digitonin; D002118:Calcium; C013289:tetraphenylphosphonium