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Updated: Aug 15, 2026
Multi-parameter Measurement of the Permeability Transition Pore Opening in Isolated Mouse Heart Mitochondria
Published on: September 7, 2012
[Effect of Ca2+ on induction of the mitochondrial pore opening in the rat myocardium]
Abstract:
The mitochondrial role opening (MPT) induced by Ca2+ has been studied in isolated rat heart mitochondria. MPT was characterized as cyclosporine A-inhibited swelling accompanied by the loss of membrane potential (deltapsim) and Ca2+ efflux after the Ca2+ -loading which was followed spectrophotometrically after the Ca2+ -arsenaso-III complex formation. It has been shown that in suspension of isolated mitochondria MPT was activated by low (with maximum at about 20 microM Ca2+) and high concentrations of Ca2+ (the concentration curve shows a saturation at about 1.0-1.5 mM). In all the cases an access of Ca2+ ions to the matrix space of the mitochondria was necessary for MPT induction. MPT activated by low concentrations of Ca2+ was accompanied by slow decrease of deltapsim and slow release of Ca2+, enhanced by ruthenium red (RR), and was independent of the substrate used (glutamate or succinate). It had not been observed if the respiratory chain was inhibited, even if the Ca2+ access to the inner mitochondrial membrane was provided by Ca2+ -ionophore A23187. At high Ca2+ concentrations rapid Ca2+ -uptake and release via Ca2+ -uniporter (inhibited by ruthenium red) followed by extensive swelling (pore formation) have been observed. It had been supposed that rapid MPT at high concentrations of Ca2+ was the result of Ca2+ entrance to the mitochondrial matrix and depolarisation of the mitochondrial membrane. The data obtained show two different mechanisms of Ca2+ -induced MPT. The one is sensitive to the redox-state of the electron transport chain and is abolished if the respiration is inhibited. The other is independent of mitochondrial respiration and needs only Ca2+ access to the inner mitochondrial membrane and Ca2+ binding to some specific sites leading to MPT opening.
Insights
Calcium ions induce mitochondrial permeability transition (MPT) through two distinct pathways in rat heart mitochondria. One pathway is respiration-dependent, while the other is independent of mitochondrial respiration.
Area of Science:
- Biochemistry
- Cell Biology
- Mitochondrial Physiology
Background:
- Mitochondrial permeability transition (MPT) is a critical process in cell death and bioenergetics.
- Calcium ions (Ca2+) are known regulators of MPT, but the precise mechanisms remain incompletely understood.
- Isolated rat heart mitochondria provide a model system to investigate Ca2+-induced MPT.
Purpose of the Study:
- To elucidate the distinct mechanisms by which Ca2+ induces MPT in isolated rat heart mitochondria.
- To characterize the roles of mitochondrial respiration and Ca2+ transport in MPT induction.
- To differentiate between low and high Ca2+ concentration effects on MPT.
Main Methods:
- Spectrophotometric monitoring of mitochondrial swelling and Ca2+ -arsenazo-III complex formation.
- Measurement of mitochondrial membrane potential (deltapsim) and Ca2+ efflux.
- Utilizing Ca2+ ionophore A23187 and ruthenium red (RR) to modulate Ca2+ transport.
- Investigating MPT under varying substrate conditions (glutamate, succinate) and respiratory chain inhibition.
Main Results:
- Ca2+ -induced MPT was observed at both low and high Ca2+ concentrations, requiring matrix Ca2+ access.
- Low Ca2+ concentrations induced slow MPT, dependent on mitochondrial respiration and sensitive to ruthenium red.
- High Ca2+ concentrations triggered rapid MPT, independent of respiration, involving Ca2+ uptake/release via the Ca2+ uniporter and pore formation.
- Two distinct Ca2+-dependent MPT mechanisms were identified: one respiration-dependent and another respiration-independent.
Conclusions:
- Ca2+ activates MPT via at least two different pathways in rat heart mitochondria.
- The observed MPT mechanisms differ in their dependence on the mitochondrial respiratory chain.
- Understanding these pathways is crucial for comprehending mitochondrial function and dysfunction in cardiac physiology and pathology.
