Abstract
Trypomastigotes of Trypanosoma cruzi maintain an intracellular Ca2+ concentration([Ca2+](i)) of 64 ± 30 nM. Equilibration of trypomastigotes in an extracellular buffer containing 0.5 mM [Ca2+]0 (preloaded cells) increased [Ca2+](i) < 20 nM whereas total cell Ca2+ increased by 1.5 to 2.0 pmole/cell. This amount of Ca2+ would be expected to increase [Ca2+](i) to > 10 μM suggesting active sequestration of Ca2+. We tested the hypothesis that maintenance of [Ca2+](i) involved both the sequestration into intracellular storage sites and extrusion into the extracellular space. Pharmacological probes known to influence [Ca2+](i) through well characterized pathways in higher eukaryotic cells were employed. [Ca2+](i) responses in the presence or absence of [Ca2+]0 were measured to asses the relative contribution of sequestration or extrusion processes in [Ca2+](i) homeostasis. In the presence of 0.5 mM [Ca2+]0, the ability of several agents to increase [Ca2+](i) was magnified in the order ionomycin >>> nigericin > thapsigargin > monensin > valinomycin. In contrast, preloading markedly enhanced the increase in [Ca2+](i) observed only in response to monensin. Manoalide, an inhibitor of phospholipase A2, enhanced the accumulation of [Ca2+](i) due to all agents tested, particularly ionomycin and thapsigargin. Our results suggest that sequestration of [Ca2+](i) involved storage sites sensitive to monensin and ionomycin whereas extrusion of Ca2+ may involve phospholipase A2 activity. A Na+/Ca2+ exchange mechanism did not appear to contribute to Ca2+ homeostasis.
Original language | English (US) |
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Pages (from-to) | 80-86 |
Number of pages | 7 |
Journal | Journal of Eukaryotic Microbiology |
Volume | 45 |
Issue number | 1 |
DOIs | |
State | Published - 1998 |
Keywords
- Chagas' disease
- Hemoflaggelates
- Ionomycin
- Manoalide
- Monensin
- Nigericin
- Thapsigargin
- V alinomycin
ASJC Scopus subject areas
- Microbiology