The fine structure of acidocalcisomes in Trypanosoma cruzi

Trypanosoma cruzi survives in vertebrate and invertebrate hosts and has dev eloped mechanisms that allow it to adapt to changes in the microenvironment such as temperature, pH, and ionic composition. Most of its calcium is con centrated in an organelle named the acidocalcisome, which is acidified by a (V-H+)adenosine triphosphatase and has H+/Ca2+ counter-transportation for calcium uptake. In this work acidocalcisomes were examined using different transmission electron microscopy techniques. In thin sections of different stages, acidocalcisomes presented a circular shape with an electron-dense i nclusion containing p(3-), Ca2+, Na+, Mg2+, K+, and Zn2+. They could be dis tinguished from gold-labeled albumin-containing reservosomes in whole epima stigotes, and a morphometric analysis showed higher amounts of these organe lles in amastigotes as compared with epimastigotes and trypomastigotes. It is possible that this variation in the amount of acidocalcisomes in the dif ferent evolutive stages could reflect adaptation mechanisms used by the par asite to survive and multiply in different environmental conditions.