Cecatto 2022 Abstract Bioblast

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Cecatto Cristiane
Cecatto Cristiane, Cardoso LHD, Gnaiger E (2022) Mitochondrial calcium uptake capacity is lower than calcium retention capacity in the presence and absence of cyclosporin A. Bioblast 2022: BEC Inaugural Conference.

Link: Bioblast 2022: BEC Inaugural Conference

Cecatto Cristiane, Cardoso Luiza HD, Gnaiger Erich (2022)

Event: Bioblast 2022

Mitochondrial calcium homeostasis plays important roles in cell survival and cell death, and its dysfunction is involved in many diseases. Mitochondria contribute to the buffering of cytosolic free calcium levels and thereby to the regulation of calcium-dependent cellular processes by uptake and storage of calcium in the form of osmotically inactive calcium phosphates in the mitochondrial matrix. Calcium retention capacity is defined as the amount of calcium titrated up to a threshold where permeability transition triggers the release of calcium and several other substances such as cytochrome c. We measured calcium uptake and respiration in mitochondria isolated from mouse liver using the Oroboros O2k with Smart Fluo-Sensors and Calcium Green. Calcium Green did not inhibit respiration. Calcium concentrations increased sharply upon stepwise 5 µM calcium titrations and declined gradually during intervals of 6 min as a result of mitochondrial calcium uptake in the LEAK state. Calcium uptake was incomplete, however, upon initial and final titrations before the onset of permeability transition, as shown by the merely partial decline of calcium concentrations in the medium. Consequently, the actual calcium uptake capacity CaUC needs to be corrected for incomplete uptake. CaUC was 45 % of the conventionally defined calcium retention capacity in controls and 55 % in the presence of cyclosporin A. These results suggest that high calcium retention capacities reported in the literature require critical evaluation and should be replaced by calcium uptake capacities properly corrected for extramitochondrial calcium concentrations measured in the medium.

Keywords: Calcium uptake, Mitochondrial permeability transition pore, Calcium green, High-resolution respirometry, Calcium retention capacity Bioblast editor: Plangger M O2k-Network Lab: AT Innsbruck Oroboros


Oroboros Instruments, Innsbruck, Austria. -cristiane.cecatto@oroboros.at

Labels: MiParea: Respiration 

Organism: Mouse  Tissue;cell: Liver  Preparation: Isolated mitochondria 

Regulation: Calcium  Coupling state: LEAK 

HRR: Oxygraph-2k, O2k-Fluorometer