Limits...
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.

Show MeSH

Related in: MedlinePlus

Transient mitochondrial depolarizations are dependent on SR calcium stores. a and b show some characteristic surface and  line images, illustrating the occurrence of flicker in a cell under control conditions. After exposure to 30 μM ryanodine (c and d), the  flicker was almost completely abolished.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2132882&req=5

Figure 7: Transient mitochondrial depolarizations are dependent on SR calcium stores. a and b show some characteristic surface and line images, illustrating the occurrence of flicker in a cell under control conditions. After exposure to 30 μM ryanodine (c and d), the flicker was almost completely abolished.

Mentions: Perhaps a more convincing functional indication of reversibility is the observation of events seen repeatedly over the same single mitochondrion; these must of necessity involve a true repolarization after each event if a further event is to occur. Such repeated events were routinely seen and are illustrated specifically in Fig. 4, a (iv) and c (see below), but they are also apparent in a number of other image sequences (Figs. 2, 5, 6, and 7).


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

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

Transient mitochondrial depolarizations are dependent on SR calcium stores. a and b show some characteristic surface and  line images, illustrating the occurrence of flicker in a cell under control conditions. After exposure to 30 μM ryanodine (c and d), the  flicker was almost completely abolished.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 7: Transient mitochondrial depolarizations are dependent on SR calcium stores. a and b show some characteristic surface and line images, illustrating the occurrence of flicker in a cell under control conditions. After exposure to 30 μM ryanodine (c and d), the flicker was almost completely abolished.
Mentions: Perhaps a more convincing functional indication of reversibility is the observation of events seen repeatedly over the same single mitochondrion; these must of necessity involve a true repolarization after each event if a further event is to occur. Such repeated events were routinely seen and are illustrated specifically in Fig. 4, a (iv) and c (see below), but they are also apparent in a number of other image sequences (Figs. 2, 5, 6, and 7).

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