Selective use of a reserved mechanism for inducing calcium oscillations

Ionomycin (IM) at 5 microM mediates the Ca(2+)/H(+) exchange, while IM at 1 microM activates the store-operated Ca(2+) entry channels (SOCs). In this study, the effects of depolarization on both pathways were examined in rat submandibular acinar cells by increasing extracellular K(+) concentration ([K(+)](o)). IM (5 microM, the Ca(2+)/H(+) exchange) increased the intracellular Ca(2+) concentration ([Ca(2+)](i)) to an extremely high value at 151 mM [K(+)](o). However, with increasing [K(+)](o), the rates of Ca(2+) entry decreased in a linear relationship. The reversal potential (E (rev)) for the Ca(2+)/H(+) exchange was +93 mV, suggesting that IM (5 microM) exchanges 1 Ca(2+) for 1 H(+). Thus, depolarization decreases the Ca(2+) influx via the Ca(2+)/H(+) exchange because of its electrogenicity (1 Ca(2+) for 1 H(+)). On the other hand, IM (1 microM, the SOCs) abolished an increase in [Ca(2+)](i) at 151 mM [K(+)](o). With increasing [K(+)](o), the rate of Ca(2+) entry immediately decreased linearly. The E (rev) for the SOC was +3.7 mV, suggesting that the SOCs are nonselective cation channels and less selective for Ca(2+) over Na(+) (P (Ca)/P (Na) = 8.2). Moreover, an increase in extracellular Ca(2+) concentration (20 mM) enhanced the Ca(2+) entry via the SOCs at 151 mM [K(+)](o), suggesting depolarization does not inhibit the SOCs and decreases the driving force for the Ca(2+) entry. This suggests that membrane potential changes induced by a secretory stimulation finely regulate the [Ca(2+)](i) via the SOCs in rat submandibular acinar cells. In conclusion, IM increases [Ca(2+)](i) via two pathways depending on its concentration, the exchange of 1 Ca(2+) for 1 H(+) at 5 muM and the SOCs at 1 microM.

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“…On the other hand, previous reports [16,17] demonstrated that an increase in [K ? ] o , such as 25-30 mM, stimulates [Ca 2? ]…”

Section: Discussionmentioning

confidence: 84%

Membrane potential modulation of ionomycin-stimulated Ca2+ entry via Ca2+/H+ exchange and SOC in rat submandibular acinar cells

et al. 2010

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“…30-130 mmol/L, osmolarity from 310 to 220 mOsm) on the functions of the acinar and different ductal cells, and the effects of any disturbances of such ordered gradients on both the physiology and pathology, have never been systematically investigated at the cellular and molecular levels. The fact that large amounts of potassium ion are secreted after stimulation of the salivary glands has long been noted, but the physiological significance of the secreted potassium has never been properly addressed [20,[25][26][27] .…”

Section: Submandibular Gland: Microanatomy Potassium and Osmolarity mentioning

confidence: 99%

“…The fact that large amounts of potassium ion are secreted after stimulation of the salivary glands has long been noted, but the physiological significance of the secreted potassium has never been properly addressed [20,[25][26][27] .…”

Section: Submandibular Gland: Microanatomy Potassium and Osmolarity mentioning

confidence: 99%

“…Additional works will be needed to reveal whether this is a general rule along the secretory axis, especially in the intro-and inter-lobular ducts. [20] …”

Section: Calcium Oscillations Along the Secretory Axis In Submandibulmentioning

confidence: 99%

“…The rodent submandibular gland acinar cells are noted to increase [Ca 2+ ] c not in the form of oscillations, especially at low stimulating concentrations, but rather in the form of graded plateaus. The rat submandibular acinar cells responded to noradrenaline or acetylcholine stimulation by plateau increase in [Ca 2+ ] c , even at the minimal or threshold stimulating concentrations used [20] . All of these works have been carried out on the isolated submandibular acini bathed in a Kreb's-like buffered solution.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cytosolic calcium oscillations in submandibular gland cells1

Yan

Zhou

et al. 2006

Acta Pharmacologica Sinica

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Calcium oscillations can, by default, encode diverse and specific signals by different modes of modulation. Frequency modulation is illustrated by the activation of calcium/calmodulin-dependent protein kinase II at unit Hz, and of calcineurin at 10 mHz frequencies, respectively. The submandibular gland secretory axis is characterized by both potassium and osmolarity gradients from the luminal side of the secretory cells. Such gradients may play significant physiological roles through the feedback modulation of cholinergic stimulation. High potassium transforms plateau calcium increases induced by cholinergic stimulation of the submandibular acinar cells into oscillatory calcium increases. The ductal cells may have similar mechanisms of feedback modulation both by high potassium and by hypoosmolarity. Such feedback mechanisms could modulate the decision-making process for determining which secretory products are selectively released after nerve stimulation.

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Substance P conjugated to CdTe quantum dots triggers cytosolic calcium concentration oscillations and induces quantum dots internalization in the pancreatic carcinoma cell line AR4-2J

et al. 2011

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Highly fluorescent CdTe quantum dots (QDs) stabilized by 3-mercaptopropionic acid were prepared by an aqueous solution approach and used as a fluorescent label to link substance P (SP) in studying the interaction of SP with NK-1 receptor, which was expressed on the AR4-2J cell line. Nonspecific adsorptions of CdTe QDs on the AR4-2J cell membrane were observed, whereas the QD-SP conjugates successfully crossed the cell membrane and entered the cytosol. SP is a neurotransmitter, and neurotransmitter-induced calcium concentration oscillation is a common phenomenon in diverse cells especially of secretory type. Cytosolic calcium concentration responses were studied in the AR4-2J cell line during stimulation with SP and QD-SP conjugates. The oscillations triggered by SP and QD-SP conjugates were dose-dependent and very similar. Such QD-SP conjugates readily internalized into the cytosol as would be expected of an active NK-1 ligand. Therefore QD-SP conjugates could be used successfully to study ligand and NK-1 receptor interactions in live cells. Our research may provide a meaningful reference for congener research.

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Selective use of a reserved mechanism for inducing calcium oscillations

Cited by 4 publications

References 35 publications

Membrane potential modulation of ionomycin-stimulated Ca2+ entry via Ca2+/H+ exchange and SOC in rat submandibular acinar cells

Membrane potential modulation of ionomycin-stimulated Ca2+ entry via Ca2+/H+ exchange and SOC in rat submandibular acinar cells

Cytosolic calcium oscillations in submandibular gland cells1

Substance P conjugated to CdTe quantum dots triggers cytosolic calcium concentration oscillations and induces quantum dots internalization in the pancreatic carcinoma cell line AR4-2J

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