Functional Role of Chromogranins

Borges, Ricardo; Machado, José David; Alonso, Carmen; Brioso, Miguel A.; Gómez, José Luís Graña

doi:10.1007/0-306-46837-9_5

Cited by 11 publications

(5 citation statements)

References 20 publications

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“…[26] Note that a similar issue potentially exists also in TIRF experiments since the intravesicular pH is approximately 5.5. [25] The corresponding pH gradient relative to the buffered extracellular medium necessarily sets thermodynamic conditions which imply a release of protons in the thin discoid electrode-prism cleft. As discussed above, a part of them may be readily captured by the buffer base while the cleft contains sufficiently of them.…”

Section: Preliminary Considerationsmentioning

confidence: 99%

“…0.6 m), [13,24,25] a comparatively huge amount of protons is released within the electrode-cell cleft during each event monitored amperometrically. Furthermore, the neutralization by the buffer of the large flux of electrochemically released protons may not occur as readily as it would happen under thermodynamic conditions because of kinetic restrictions due to the thin volume in which these protons are released.…”

Section: Preliminary Considerationsmentioning

confidence: 99%

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Prediction of Local pH Variations during Amperometric Monitoring of Vesicular Exocytotic Events at Chromaffin Cells

et al. 2010

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Electrochemical monitoring of the exocytosis process is generally performed through amperometric oxidation of the electroactive messengers released by single living cells. Herein, we consider the vesicular release of catecholamines by chromaffin cells. Each exocytotic event is thus detected as a current spike whose morphology (intensity, duration, area, etc.) features the efficiency of the secretion process. However, the electrochemical oxidation of catechols produces quinone derivatives and protons. As a consequence, unless specific mechanisms may be adopted by a cell to regulate the pH near its membrane, the local pH between the cell membrane and the electrode necessarily drops within the electrode-cell cleft. Though this consequence of amperometric detection is generally ignored, it has been investigated in this work through simulation of the local pH drop created during the amperometric recording of a sequence of exocytotic events. This was performed based on frequencies and magnitudes of release detected at chromaffin cells. The corresponding acidification was shown to severely depend on the microelectrode radius. For usual 10 μm diameter carbon fiber electrodes, pH values below six were predicted to be reached within the electrode-cell cleft after monitoring a few current spikes.

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Section: Preliminary Considerationsmentioning

confidence: 99%

Section: Preliminary Considerationsmentioning

confidence: 99%

Prediction of Local pH Variations during Amperometric Monitoring of Vesicular Exocytotic Events at Chromaffin Cells

et al. 2010

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“…[23] In chromaffin cells, secretory vesicles are essentially dense core vesicles, and consequently they are filled with a complex polyelectrolytic matrix, which stores the catecholamine molecules by collapsing around them, since Hbonding-favorable interactions compensate dipole-dipole repulsion. [39] When the matrix surface is in contact with the extracellular medium, catecholamine cations leave the matrix. The ensuing cation exchanges maintain the matrix electroneutrality but results in the progressive suppression of the H-bond network.…”

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confidence: 99%

Vesicular Exocytosis under Hypotonic Conditions Shows Two Distinct Populations of Dense Core Vesicles in Bovine Chromaffin Cells

et al. 2007

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Several previous reports have discussed the effects of external osmolarity on vesicular exocytotic processes. However, few of these studies considered hypotonic conditions on chromaffin cells. Herein, the exocytosis of catecholamines by chromaffin cells was investigated in a medium of low osmolarity (200 mOsm) by amperometry at carbon fiber microelectrodes. It is observed that the frequency of the exocytotic events is significantly higher under hypotonic conditions than under physiological conditions (315 mOsm). This further confirms that the swelling of the polyelectrolytic matrix (which follows ionic exchanges) contained in dense core vesicles is the energetic driving force of the exocytotic phenomenon, being favored by a lower osmolarity. The mean amount of catecholamines released during secretory events also increases importantly under the hypotonic condition. This may be rationalized by the coexistence of two distinct populations of dense core vesicles with a relative content ratio of 4.7. The larger content population is favored under hypotonic conditions but plays only a side role under isotonic conditions.

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“…Moreover, since in chromaffin cells secretory vesicles are essentially dense-core, [50] external osmolarity also affects ionic exchange between the matrix and the extracellular medium (i.e. swelling of the polyelectrolyte gel).…”

Section: Concomitant and Cooperative Effects On Cell Membrane Propertmentioning

confidence: 99%

“…20 mm). [50] The different interactions (electrostatic forces, chemical complexation, and hydrogen bonds) in the matrix contribute to compaction of the structure and to osmotic inactivation of its contents. [51] Then, this matrix may undergo drastic structural and topological modifications, such as swelling or compaction, when these interactions are modified owing to their exposure to a different medium (see below).…”

Section: Role Of the Dense-core Granule Of Secretory Vesicles During mentioning

confidence: 99%

The Nature and Efficiency of Neurotransmitter Exocytosis also Depend on Physicochemical Parameters

et al. 2007

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Exocytosis is an important biological process used by cells to deliver messengers or effectors to target cells with high spatial, quantitative, and kinetic precision. This process occurs by interaction and fusion of vesicles containing the (bio)chemical information with the cell membrane to release their contents into the surrounding medium. Because of its importance for life, this mechanism underlies many biological controlling factors, including different families of proteins and enzymes. Tremendous efforts have been made over the last decade toward their determination. However, in parallel, many studies have also shown that the physical and chemical characteristics of the exocytosis actors (vesicle, membrane, and extracellular medium) could directly affect the quantitative or kinetic features of secretion. The major pieces evidence for this influence, which have been reported in the literature, are reviewed herein. It demonstrates undoubtedly that pure biological aspects cannot be segregated from the physicochemical context of living mechanisms.

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Functional Role of Chromogranins

Cited by 11 publications

References 20 publications

Prediction of Local pH Variations during Amperometric Monitoring of Vesicular Exocytotic Events at Chromaffin Cells

Prediction of Local pH Variations during Amperometric Monitoring of Vesicular Exocytotic Events at Chromaffin Cells

Vesicular Exocytosis under Hypotonic Conditions Shows Two Distinct Populations of Dense Core Vesicles in Bovine Chromaffin Cells

The Nature and Efficiency of Neurotransmitter Exocytosis also Depend on Physicochemical Parameters

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