Cytosolic-free calcium in smooth-muscle and endothelial cells in an intact arterial wall from rat mesenteric artery in vitro

Oishi, Hirotaka; Budel, Stephane; Schuster, Alexander; Stergiopulos, Nikolaos; Meister, Jean-Jacques; Bény, Jean‐Louis

doi:10.1054/ceca.2001.0233

Cited by 34 publications

(43 citation statements)

References 20 publications

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“…The mechanism responsible for elevations in smooth muscle cAMP levels, which may additionally enhance electrotonic conduction through the media, is less clear. Possibilities include: (i) diffusion of endothelium-derived cAMP into subjacent smooth muscle cells via gap junctions (13), (ii) hyperpolarization-induced reductions in smooth muscle [Ca 2ϩ ] i , which could in theory activate the Ca 2ϩ -inhibited type V and VI adenylyl cyclase isoforms and͞or suppress the Ca 2ϩ -stimulated type I phosphodiesterase (23,(37)(38)(39), and (iii) transfer via gap junctions of a novel mediator produced within the endothelium that stimulates adenylyl cyclase or inhibits cAMP hydrolysis within smooth muscle (10,11). Each of these possibilities would be consistent with the observation that Gap 27 was able to prevent cAMP accumulation in iliac artery rings with intact endothelium.…”

Section: Discussionmentioning

confidence: 99%

cAMP facilitates EDHF-type relaxations in conduit arteries by enhancing electrotonic conduction via gap junctions

Griffith

Chaytor

Taylor

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

106

109

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We have investigated the role of cAMP in NO-and prostanoidindependent relaxations that are widely attributed to an endothelium-derived hyperpolarizing factor (EDHF). Under control conditions EDHF-type relaxations evoked by acetylcholine (ACh) in rabbit iliac arteries were transient, but in the presence of the cAMP phosphodiesterase inhibitor isobutylmethylxanthine (IBMX) or the cell permeant cAMP analog 8-bromo-cAMP, relaxations became sustained with their maxima potentiated Ϸ2-fold. Relaxation was associated with transient Ϸ1.5-fold elevations in smooth muscle cAMP levels with both mechanical and nucleotide responses being abolished by interrupting gap junctional communication with the connexin-mimetic peptide Gap 27 and by endothelial denudation. However, IBMX induced a sustained endothelium-independent Ϸ2-fold rise in cAMP levels, which was not further amplified by ACh, suggesting that the contribution of cAMP to the EDHF phenomenon is permissive. After selective loading of the endothelium with calcein AM, direct transfer of dye from the endothelium to the media was enhanced by IBMX or 8-bromo-cAMP, but not by 8-bromo-cGMP, whereas Gap 27 promoted sequestration within the intima. ACh-induced hyperpolarizations of subintimal smooth muscle in arterial strips with intact endothelium were abolished by Gap 27 and the adenylyl cyclase inhibitor 2 ,5 -dideoxyadenosine but were unaffected by IBMX. By contrast, in strips partially denuded of endothelium, IBMX enhanced the transmission of hyperpolarization from the endothelium to remote smooth muscle cells. These findings support the hypothesis that endothelial hyperpolarization underpins the EDHF phenomenon, with cAMP governing subsequent electrotonic signaling via both myoendothelial and homocellular smooth muscle gap junctions.connexin ͉ acetylcholine ͉ IBMX ͉ 8-bromo-cAMP ͉ cGMP

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Section: Discussionmentioning

confidence: 99%

cAMP facilitates EDHF-type relaxations in conduit arteries by enhancing electrotonic conduction via gap junctions

Griffith

Chaytor

Taylor

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

106

109

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“…The selective · 1 agonist PE, stimulates direct smooth muscle depolarization and contraction in the rat mesenteric artery, it has no direct action on the endothelial cells [16,17,37]. So both KCl and PE would be expected to depolarize endothelial cells, either directly or indirectly via smooth muscle cells [38].…”

Section: Regulation Of Endothelial Ca 2+ Events Via Myoendothelial Gamentioning

confidence: 99%

“…In addition to current passing between these cells through myoendothelial connections, there is also evidence for Ca 2+ signalling following elevations in smooth muscle cell Ca 2+ by agonists such as phenylephrine (PE) and KCl. The consequent secondary rise in endothelial Ca 2+ can enhance the production of both NO and EDHF [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Enhanced spontaneous Ca2+ events in endothelial cells reflect signalling through myoendothelial gap junctions in pressurized mesenteric arteries

2008

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SummaryIncreases in global Ca 2+ in the endothelium are a crucial step in releasing relaxing factors to modulate arterial tone. In the present study we investigated spontaneous Ca 2+ events in endothelial cells, and the contribution of smooth muscle cells to these Ca 2+ events, in pressurized rat mesenteric resistance arteries. Spontaneous Ca 2+ events were observed under resting conditions in 34% of cells. These Ca 2+ events were absent in arteries preincubated with either cyclopiazonic acid or U-73122, but were unaffected by ryanodine or nicotinamide. Stimulation of smooth muscle cell depolarization and contraction with either phenylephrine or high concentrations of KCl significantly increased the frequency of endothelial cell Ca 2+ events. The putative gap junction uncouplers carbenoxolone and 18· -glycyrrhetinic acid each inhibited spontaneous and evoked Ca 2+ events, and the movement of calcein from endothelial to smooth muscle cells. In addition, spontaneous Ca 2+ events were diminished by nifedipine, lowering extracellular Ca 2+ levels, or by blockers of non-selective Ca 2+ influx pathways. These findings suggest that in pressurized rat mesenteric arteries, spontaneous Ca 2+ events in the endothelial cells appear to originate from endoplasmic reticulum IP 3 receptors, and are subject to regulation by surrounding smooth muscle cells via myoendothelial gap junctions, even under basal conditions.

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“…Oscillations were defined as repetitive fluctuations in fluorescence a minimum of 20% above the basal Ca 2+ dependent fluorescent values. The presence of spontaneous oscillations in A7r5 cells was confirmed using different Ca 2+ -sensitive fluorophores, including Fluo-4, Fluo-3, Calcium Crimson, Calcium Orange, Calcium Green, Oregon Green, and ratiometric methods using Fluo-4 and Fura-Red [20,21]. The oscillations were synchronized among confluent cells.…”

Section: Spontaneous Ca 2+ Oscillations In the Nucleusmentioning

confidence: 79%

“…-sensitive indicators used in these experiments were fluo-4 and fura-red (Molecular Probes, Eugene, OR) [20,21]. While other indicators were tested (fluo-3, calcium orange, calcium green, calcium crimson, indo-1, and oregon Green; Molecular Probes), the ratiometric fluo-4/fura-red combination provided the most consistent results as fura-red fluorescence emission is quenched when Ca 2+ increases, while fluo-4 fluorescence increases, thus artifacts due to movement or dye sequestration are avoided [31].…”

Section: +mentioning

confidence: 99%

Spontaneous Ca2+ oscillations in subcellular compartments of vascular smooth muscle cells rely on different Ca2+ pools

et al. 2004

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Spontaneous Ca 2+ oscillations in vascular smooth muscle cells have been modeled using a single Ca 2+ pool. This report describes spontaneous Ca 2+ oscillations dependent on two separate Ca 2+ sources for the nuclear versus cytoplasmic compartments. Changes in free intracellular Ca 2+ were monitored with ratiometric Ca 2+-fluorophores using confocal microscopy. On average, spontaneous oscillations developed in 79% of rat aortic smooth muscle cells that were synchronous between the cytoplasm and nucleus. Reduction of extracellular Ca 2+ (< 1 µM) decreased the frequency and amplitude of the cytoplasmic oscillations with 48% of the oscillations asynchronous between the nuclear and cytoplasmic compartments. Similar results were obtained with the Ca 2+ channel blockers, nimodipine and diltiazem. Arg-vasopressin (AVP) induced a rapid release of intracellular Ca 2+ stores that was greater in the nuclear compartment (4.20 ± 0.23 ratio units, n = 56) than cytoplasm (2.54 ± 0.28) in cells that had spontaneously developed prior oscillations. Conversely, cells in the same conditions lacking oscillations had a greater AVP-induced Ca 2+ transient in the cytoplasm (4.99 ± 0.66, n = 17) than in the nucleus (2.67 ± 0.29). Pre-treatment with Ca 2+ channel blockers depressed the AVP responses in both compartments with the cytoplasmic Ca 2+ most diminished. Depletion of internal Ca 2+ stores prior to AVP exposure blunted the nuclear response, mimicking the response of cells that lacked prior oscillations. Spontaneous oscillating cells had a greater sarcoplasmic reticulum network than cells that did not oscillate. We propose that spontaneous nuclear oscillations rely on perinuclear sarcoplasmic reticulum stores, while the cytoplasmic oscillations rely on Ca 2+ influx.

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Cytosolic-free calcium in smooth-muscle and endothelial cells in an intact arterial wall from rat mesenteric artery in vitro

Cited by 34 publications

References 20 publications

cAMP facilitates EDHF-type relaxations in conduit arteries by enhancing electrotonic conduction via gap junctions

cAMP facilitates EDHF-type relaxations in conduit arteries by enhancing electrotonic conduction via gap junctions

Enhanced spontaneous Ca2+ events in endothelial cells reflect signalling through myoendothelial gap junctions in pressurized mesenteric arteries

Spontaneous Ca2+ oscillations in subcellular compartments of vascular smooth muscle cells rely on different Ca2+ pools

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