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|Type:||Artigo de periódico|
|Title:||Regulation Of Intracellular Calcium Homeostasis In Trypanosoma Cruzi. Effects Of Calmidazolium And Trifluoperazine|
|Abstract:||Trypanosoma cruzi epimastigotes maintained an intracellular free calcium concentration of about 0.15 μM, as measured with the fluorescent indicator Fura-2. The maintenance of low [Ca2+]i is energy-dependent since it is disrupted by KCN and FCCP. When the cells were permeabilized with digitonin, the steady-state free Ca2+ concentration in the absence of ATP was about 0.7 μM. The additional presence of ATP resulted in a steady-state level close to 0.1-0.2 μM which compares favorably with the concentration detected in intact cells. Intracellular Ca2+ uptake at high levels of free Ca2+ (1 μM) was due to energy-dependent mitochondrial uptake as indicated by its FCCP-sensitivity. However, as the free Ca2+ concentration was lowered from 1 μM, essentially all uptake was due to the ATP-dependent Ca2+ sequestration by the endoplasmic reticulum as indicated by its stimulation by ATP, and its inhibition by sodium vanadate. High concentrations of the calrnodulin antagonist trifluoperazine, inhibited both the Ca2+ uptake by the endoplasmic retlculum and by the mitochondria, while calmidazolium released Ca2+ from both compartments. In addition, trifluoperazine and calmidazolium inhibited respiration and collapsed the mitochondrial membrane potential of T. cruzi, thus indicating non-specific effects unrelated to calmodulin. © 1991.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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