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Transient mitochondrial depolarizations reflect focal sarcoplasmic reticular calcium release in single rat cardiomyocytes.

Duchen MR, Leyssens A, Crompton M - J. Cell Biol. (1998)

Bottom Line: Here we demonstrate that the mitochondrial flicker was directly related to the focal release of calcium from sarcoplasmic reticular (SR) calcium stores and consequent uptake of calcium by local mitochondria.Thus, the events were dramatically reduced by (a) depletion of SR calcium stores after long-term incubation in EGTA or thapsigargin (500 nM); (b) buffering intracellular calcium using BAPTA-AM loading; (c) blockade of SR calcium release with ryanodine (30 microM); and (d) blockade of mitochondrial calcium uptake by microinjection of diaminopentane pentammine cobalt (DAPPAC), a novel inhibitor of the mitochondrial calcium uniporter.These observations demonstrate that focal SR calcium release results in calcium microdomains sufficient to promote local mitochondrial calcium uptake, suggesting a tight coupling of calcium signaling between SR release sites and nearby mitochondria.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University College London, London WC1E 6BT, United Kingdom. m.duchen@ucl.ac.uk

ABSTRACT
Digital imaging of mitochondrial potential in single rat cardiomyocytes revealed transient depolarizations of mitochondria discretely localized within the cell, a phenomenon that we shall call "flicker." These events were usually highly localized and could be restricted to single mitochondria, but they could also be more widely distributed within the cell. Contractile waves, either spontaneous or in response to depolarization with 50 mM K+, were associated with propagating waves of mitochondrial depolarization, suggesting that propagating calcium waves are associated with mitochondrial calcium uptake and consequent depolarization. Here we demonstrate that the mitochondrial flicker was directly related to the focal release of calcium from sarcoplasmic reticular (SR) calcium stores and consequent uptake of calcium by local mitochondria. Thus, the events were dramatically reduced by (a) depletion of SR calcium stores after long-term incubation in EGTA or thapsigargin (500 nM); (b) buffering intracellular calcium using BAPTA-AM loading; (c) blockade of SR calcium release with ryanodine (30 microM); and (d) blockade of mitochondrial calcium uptake by microinjection of diaminopentane pentammine cobalt (DAPPAC), a novel inhibitor of the mitochondrial calcium uniporter. These observations demonstrate that focal SR calcium release results in calcium microdomains sufficient to promote local mitochondrial calcium uptake, suggesting a tight coupling of calcium signaling between SR release sites and nearby mitochondria.

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Quantitative comparisons between manipulations. The histogram illustrates the mean values  obtained for the signal measured over the images averaged from time series under  each of the conditions discussed and indicated below  the columns. The number of  cells from which the values  were derived are indicated  by each column. Significance  at the level of <0.05 is indicated by * and at the level of  0.001 by **.
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Figure 9: Quantitative comparisons between manipulations. The histogram illustrates the mean values obtained for the signal measured over the images averaged from time series under each of the conditions discussed and indicated below the columns. The number of cells from which the values were derived are indicated by each column. Significance at the level of <0.05 is indicated by * and at the level of 0.001 by **.

Mentions: The quantitative results of all the manipulations described above are summarized in Fig. 9.


Transient mitochondrial depolarizations reflect focal sarcoplasmic reticular calcium release in single rat cardiomyocytes.

Duchen MR, Leyssens A, Crompton M - J. Cell Biol. (1998)

Quantitative comparisons between manipulations. The histogram illustrates the mean values  obtained for the signal measured over the images averaged from time series under  each of the conditions discussed and indicated below  the columns. The number of  cells from which the values  were derived are indicated  by each column. Significance  at the level of <0.05 is indicated by * and at the level of  0.001 by **.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132882&req=5

Figure 9: Quantitative comparisons between manipulations. The histogram illustrates the mean values obtained for the signal measured over the images averaged from time series under each of the conditions discussed and indicated below the columns. The number of cells from which the values were derived are indicated by each column. Significance at the level of <0.05 is indicated by * and at the level of 0.001 by **.
Mentions: The quantitative results of all the manipulations described above are summarized in Fig. 9.

Bottom Line: Here we demonstrate that the mitochondrial flicker was directly related to the focal release of calcium from sarcoplasmic reticular (SR) calcium stores and consequent uptake of calcium by local mitochondria.Thus, the events were dramatically reduced by (a) depletion of SR calcium stores after long-term incubation in EGTA or thapsigargin (500 nM); (b) buffering intracellular calcium using BAPTA-AM loading; (c) blockade of SR calcium release with ryanodine (30 microM); and (d) blockade of mitochondrial calcium uptake by microinjection of diaminopentane pentammine cobalt (DAPPAC), a novel inhibitor of the mitochondrial calcium uniporter.These observations demonstrate that focal SR calcium release results in calcium microdomains sufficient to promote local mitochondrial calcium uptake, suggesting a tight coupling of calcium signaling between SR release sites and nearby mitochondria.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University College London, London WC1E 6BT, United Kingdom. m.duchen@ucl.ac.uk

ABSTRACT
Digital imaging of mitochondrial potential in single rat cardiomyocytes revealed transient depolarizations of mitochondria discretely localized within the cell, a phenomenon that we shall call "flicker." These events were usually highly localized and could be restricted to single mitochondria, but they could also be more widely distributed within the cell. Contractile waves, either spontaneous or in response to depolarization with 50 mM K+, were associated with propagating waves of mitochondrial depolarization, suggesting that propagating calcium waves are associated with mitochondrial calcium uptake and consequent depolarization. Here we demonstrate that the mitochondrial flicker was directly related to the focal release of calcium from sarcoplasmic reticular (SR) calcium stores and consequent uptake of calcium by local mitochondria. Thus, the events were dramatically reduced by (a) depletion of SR calcium stores after long-term incubation in EGTA or thapsigargin (500 nM); (b) buffering intracellular calcium using BAPTA-AM loading; (c) blockade of SR calcium release with ryanodine (30 microM); and (d) blockade of mitochondrial calcium uptake by microinjection of diaminopentane pentammine cobalt (DAPPAC), a novel inhibitor of the mitochondrial calcium uniporter. These observations demonstrate that focal SR calcium release results in calcium microdomains sufficient to promote local mitochondrial calcium uptake, suggesting a tight coupling of calcium signaling between SR release sites and nearby mitochondria.

Show MeSH
Related in: MedlinePlus