Simultaneous measurement of mitochondrial calcium and mitochondrial membrane potential in live cells by fluorescent microscopy

Matthew McKenzie, Sze C. Lim, Michael R. Duchen

Research output: Contribution to journalArticleOtherpeer-review

18 Citations (Scopus)


Apart from their essential role in generating ATP, mitochondria also act as local calcium (Ca2+) buffers to tightly regulate intracellular Ca2+ concentration. To do this, mitochondria utilize the electrochemical potential across their inner membrane (ΔΨm) to sequester Ca2+. The influx of Ca2+ into the mitochondria stimulates three rate-limiting dehydrogenases of the citric acid cycle, increasing electron transfer through the oxidative phosphorylation (OXPHOS) complexes. This stimulation maintains ΔΨm, which is temporarily dissipated as the positive calcium ions cross the mitochondrial inner membrane into the mitochondrial matrix. We describe here a method for simultaneously measuring mitochondria Ca2+ uptake and ΔΨm in live cells using confocal microscopy. By permeabilizing the cells, mitochondrial Ca2+ can be measured using the fluorescent Ca2+ indicator Fluo-4, AM, with measurement of ΔΨm using the fluorescent dye tetramethylrhodamine, methyl ester, perchlorate (TMRM). The benefit of this system is that there is very little spectral overlap between the fluorescent dyes, allowing accurate measurement of mitochondrial Ca2+ and ΔΨm simultaneously. Using the sequential addition of Ca2+ aliquots, mitochondrial Ca2+ uptake can be monitored, and the concentration at which Ca2+ induces mitochondrial membrane permeability transition and the loss of ΔΨm determined.

Original languageEnglish
Article numbere55166
Number of pages6
JournalJournal of Visualized Experiments
Issue number119
Publication statusPublished - 24 Jan 2017


  • Calcium
  • Cellular biology
  • Confocal microscopy
  • Fluorescent staining
  • Issue 119
  • Live cells
  • Membrane potential
  • Mitochondria

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