Docampo R, Vercesi A E
Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, Cidade Universitária, Brazil.
J Biol Chem. 1989 Jan 5;264(1):108-11.
The use of digitonin to permeabilize Trypanosoma cruzi plasma membrane enabled us to study Ca2+ transport and oxidative phosphorylation in mitochondria in situ. Addition of Ca2+ to these preparations evoked a cycle of respiratory stimulation. Ca2+ uptake was partially inhibited by ruthenium red, almost totally inhibited by antimycin A, and stimulated by inorganic phosphate. Addition of carbonyl cyanide p-trifluoromethoxyphenylhydrazone to digitonin-permeabilized T. cruzi epimastigotes under steady-state conditions was followed by Ca2+ release. Antimycin A- and carbonyl cyanide p-trifluoromethoxyphenylhydrazonein-sensitive Ca2+ uptake was also detected in digitonin-permeabilized epimastigotes. Accordingly, ATP stimulated Ca2+ uptake by preparations de-energized by oligomycin and antimycin A. In conclusion, in contrast to previous reports indicating that a Ca2+ transport system occurs only in mitochondria from vertebrate tissues, T. cruzi epimastigotes also possess a similar system. In addition, these protozoan mitochondria have an extremely high resistance to the deleterious effects of massive Ca2+ loads in comparison with most types of mammalian mitochondria.
使用洋地黄皂苷使克氏锥虫的质膜通透，这使我们能够原位研究线粒体中的钙离子运输和氧化磷酸化。向这些制剂中添加钙离子会引发呼吸刺激循环。钙离子摄取部分受钌红抑制，几乎完全受抗霉素A抑制，并受无机磷酸盐刺激。在稳态条件下，向经洋地黄皂苷通透处理的克氏锥虫前鞭毛体中添加羰基氰化物对三氟甲氧基苯腙后会导致钙离子释放。在经洋地黄皂苷通透处理的前鞭毛体中也检测到了对抗霉素A和羰基氰化物对三氟甲氧基苯腙敏感的钙离子摄取。因此，ATP刺激了经寡霉素和抗霉素A去能的制剂对钙离子的摄取。总之，与之前表明钙离子运输系统仅存在于脊椎动物组织线粒体中的报道相反，克氏锥虫前鞭毛体也拥有类似的系统。此外，与大多数类型的哺乳动物线粒体相比，这些原生动物线粒体对大量钙离子负荷的有害影响具有极高的抗性。
