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|Type:||Artigo de periódico|
|Title:||Calcium Homeostasis In Trypanosoma Cruzi Amastigotes: Presence Of Inositol Phosphates And Lack Of An Inositol 1,4,5-trisphosphate-sensitive Calcium Pool|
|Abstract:||The permeabilization of Trypanosoma cruzi amastigotes with digitonin allowed the study of Ca2+ fluxes between intracellular organelles in situ. In addition, fura-2 was used to determine the cytosolic Ca2+ concentration in the intact cells. When amastigotes were permeabilized in a reaction medium containing MgATP, succinate and 3.5 μM Ca2+, they lowered the medium Ca2+ concentration to the submicromolar level, a range which correlates favorably with that detected in the intact cells with fura-2. The presence of 1 μM FCCP strongly decreased the initial rate of Ca2+ sequestration by these permeabilized cells. This FCCP-insensitive Ca2+ uptake, probably represented by the endoplasmic reticulum, was completely inhibited by 500 μM vanadate. On the other hand, when vanadate instead of FCCP was present, the initial rate of Ca2+ accumulation was decreased and the Ca2+ set point was increased to about 0.8 μM. The succinate dependence and FCCP sensitivity of the later Ca2+ uptake indicate that it may be exerted by the mitochondria. Despite the presence of inositol phosphates, as determined by [3H]inositol incorporation, and of a large extramitochondrial Ca2+ pool, no IP3-sensitive or thapsigargin-sensitive Ca2+ release could be detected in either amastigotes or epimastigotes. © 1992.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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