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1.
Effects of intracellular Mg2+ on a native Ca2+-and voltage-sensitive large-conductance K+ channel in cultured human renal proximal tubule cells were examined with the patch-clamp technique in the inside-out mode.
At an intracellular concentration of Ca2+ ([Ca2+]i) of 10−5–10−4 M, addition of 1–10 mM Mg2+ increased the open probability (Po) of the channel, which shifted the Po –membrane potential (Vm) relationship to the negative voltage direction without causing an appreciable change in the gating charge (Boltzmann constant).
However, the Mg2+-induced increase in Po was suppressed at a relatively low [Ca2+]i (10−5.5–10−6 M). Dwell-time histograms have revealed that addition of Mg2+ mainly increased Po by extending open times at 10−5 M Ca2+ and extending both open and closed times simultaneously at 10−5.5 M Ca2+. Since our data showed that raising the [Ca2+]i from 10−5 to 10−4 M increased Po mainly by shortening the closed time, extension of the closed time at 10−5.5 M Ca2+ would result from the Mg2+-inhibited Ca2+-dependent activation. At a constant Vm, adding Mg2+ enhanced the sigmoidicity of the Po–[Ca2+]i relationship with an increase in the Hill coefficient. These results suggest that the major action of Mg2+ on this channel is to elevate Po by lengthening the open time, while extension of the closed time at a relatively low [Ca2+]i results from a lowering of the sensitivity to Ca2+ of the channel by Mg2+, which causes the increase in the Hill coefficient.
M. Kubokawa and Y. Sohma contributed equally to this work. 相似文献
2.
Long LH Liu J Liu RL Wang F Hu ZL Xie N Fu H Chen JG 《Cellular and molecular neurobiology》2009,29(1):7-15
Methionine and cysteine residues in proteins are the major targets of reactive oxygen species (ROS). The present work was
designed to characterize the impact of methionine and cysteine oxidation upon [Ca2+]i in hippocampal neurons. We investigated the effects of H2O2 and chloramine T(Ch-T) agents known to oxidize both cysteine and methionine residues, and 5, 5′-dithio-bis (2-nitrobenzoic
acid) (DTNB)—a cysteine-specific oxidant, on the intracellular calcium in hippocampal neurons. The results showed that these
three oxidants, 1 mM H2O2, 1 mM Ch-T, and 500 μM DTNB, induced an sustained elevation of [Ca2+]i by 76.1 ± 3.9%, 86.5 ± 5.0%, and 24.4 ± 3.2% over the basal level, respectively. The elevation induced by H2O2 and Ch-T was significantly higher than DTNB. Pretreatment with reductant DTT at 1 mM for 10 min completely prevented the
action of DTNB on [Ca2+]i, but only partially reduced the effects of H2O2 and Ch-T on [Ca2+]i, the reductions were 44.6 ± 4.2% and 29.6 ± 6.1% over baseline, respectively. The elevation of [Ca2+]i induced by H2O2 and Ch-T after pretreatment with DTT were statistically higher than that induced by single administration of DTNB. Further
investigation showed that the elevation of [Ca2+]i mainly resulted from internal calcium stores. From our data, we propose that methionine oxidation plays an important role
in the regulation of intracellular calcium and this regulation may mainly be due to internal calcium stores. 相似文献
3.
Summary Discrepancies about the role of L-type voltage-gated calcium channels (VGCC) in acetylcholine (ACh)-induced [Ca2+]i oscillations in tracheal smooth muscle cells (TSMCs) have been seen in recent reports. We demonstrate here that ACh-induced
[Ca2+]i oscillations in TMCS were reversibly inhibited by three VGCC blockers, nicardipine, nifedipine and verapamil. Prolonged (several
minutes) application of VGCC blockers, led to tachyphylaxis; that is, [Ca2+]i oscillations resumed, but at a lower frequency. Brief (15–30 s) removal of VGCC blockers re-sensitized [Ca2+]i oscillations to inhibition by the agents. Calcium oscillations tolerant to VGCC blockers were abolished by KB-R7943, an inhibitor
of the reverse mode of Na+/Ca2+ exchanger (NCX). KB-R7943 alone also abolished ACh-induced [Ca2+]i oscillations. Enhancement of the reverse mode of NCX via removing extracellular Na+ reversed inhibition of ACh-induced [Ca2+]i oscillations by VGCC blockers. Inhibition of non-selective cation channels using Gd3+ slightly reduced the frequency of ACh-induced [Ca2+]i oscillations, but did not prevent the occurrence of tachyphylaxis. Altogether, these results suggest that VGCC and the reverse
mode of NCX are two primary Ca2+ entry pathways for maintaining ACh-induced [Ca2+]i oscillations in TSMCs. The two pathways complement each other, and may account for tachyphylaxis of ACh-induced [Ca2+]i oscillations to VGCC blockers. 相似文献
4.
Background
Although various endothelium-dependent relaxing factors (endothelial autacoids) are released upon the elevation of endothelial cytosolic free Ca2+ concentration (EC [Ca2+]i), the quantitative relationship between EC [Ca2+]i and vascular tone remains to be established. Moreover, whether the basal release of endothelial autacoids is modulated by basal EC [Ca2+]i is still unclear. We assessed these issues by using a novel method that allows simultaneous recording of EC [Ca2+]i and vascular displacement in dissected rat aortic segments. 相似文献5.
The anoxia-dependent elevation of cytosolic Ca2+ concentration, [Ca2+]cyt, was investigated in plants differing in tolerance to hypoxia. The [Ca2+]cyt was measured by fluorescence microscopy in single protoplasts loaded with the calcium-fluoroprobe Fura 2-AM. Imposition of
anoxia led to a fast (within 3 min) significant elevation of [Ca2+]cyt in rice leaf protoplasts. A tenfold drop in the external Ca2+ concentration (to 0.1 mM) resulted in considerable decrease of the [Ca2+]cyt shift. Rice root protoplasts reacted upon anoxia with higher amplitude. Addition of plasma membrane (verapamil, La3+ and EGTA) and intracellular membrane Ca2+-channel antagonists (Li+, ruthenium red and cyclosporine A) reduced the anoxic Ca2+-accumulation in rice. Wheat protoplasts responded to anoxia by smaller changes of [Ca2+]cyt. In wheat leaf protoplasts, the amplitude of the Ca2+-shift little depended on the external level of Ca2+. Wheat root protoplasts were characterized by a small shift of [Ca2+]cyt under anoxia. Plasmalemma Ca2+-channel blockers had little effect on the elevation of cytosolic Ca2+ in wheat protoplasts. Intact rice seedlings absorbed Ca2+ from the external medium under anoxic treatment. On the contrary, wheat seedlings were characterized by leakage of Ca2+. Verapamil abolished the Ca2+ influx in rice roots and Ca2+ efflux from wheat roots. Anoxia-induced [Ca2+]cyt elevation was high particularly in rice, a hypoxia-tolerant species. In conclusion, both external and internal Ca2+ stores are important for anoxic [Ca2+]cyt elevation in rice, whereas the hypoxia-intolerant wheat does not require external sources for [Ca2+]cyt rise. Leaf and root protoplasts similarly responded to anoxia, independent of their organ origin. 相似文献
6.
Craviso GL Choe S Chatterjee P Chatterjee I Vernier PT 《Cellular and molecular neurobiology》2010,30(8):1259-1265
Exposing bovine chromaffin cells to a single 5 ns, high-voltage (5 MV/m) electric pulse stimulates Ca2+ entry into the cells via L-type voltage-gated Ca2+ channels (VGCC), resulting in the release of catecholamine. In this study, fluorescence imaging was used to monitor nanosecond
pulse-induced effects on intracellular Ca2+ level ([Ca2+]i) to investigate the contribution of other types of VGCCs expressed in these cells in mediating Ca2+ entry. ω-Conotoxin GVIA and ω-agatoxin IVA, antagonists of N-type and P/Q-type VGCCs, respectively, reduced the magnitude
of the rise in [Ca2+]i elicited by a 5 ns pulse. ω-conotoxin MVIIC, which blocks N- and P/Q-type VGCCs, had a similar effect. Blocking L-, N-, and
P\Q-type channels simultaneously with a cocktail of VGCC inhibitors abolished the pulse-induced [Ca2+]i response of the cells, suggesting Ca2+ influx occurs only via VGCCs. Lowering extracellular K+ concentration from 5 to 2 mM or pulsing cells in Na+-free medium suppressed the pulse-induced rise in [Ca2+]i in the majority of cells. Thus, both membrane potential and Na+ entry appear to play a role in the mechanism by which nanoelectropulses evoke Ca2+ influx. However, activation of voltage-gated Na+ channels (VGSC) is not involved since tetrodotoxin (TTX) failed to block the pulse-induced rise in [Ca2+]i. These findings demonstrate that a single electric pulse of only 5 ns duration serves as a novel stimulus to open multiple
types of VGCCs in chromaffin cells in a manner involving Na+ transport across the plasma membrane. Whether Na+ transport occurs via non-selective cation channels and/or through lipid nanopores remains to be determined. 相似文献
7.
Subtypes of purinergic receptors involved in modulation of cytoplasmic calcium ion concentration ([Ca2+]i) and insulin release in mouse pancreatic β-cells were examined in two systems, pancreatic islets in primary culture and beta-TC6
insulinoma cells. Both systems exhibited some physiological responses such as acetylcholine-stimulated [Ca2+]i rise via cytoplasmic Ca2+ mobilization. Addition of ATP, ADP, and 2-MeSADP (each 100 μM) transiently increased [Ca2+]i in single islets cultured in the presence of 5.5 mM (normal) glucose. The potent P2Y1 receptor agonist 2-MeSADP reduced insulin secretion significantly in islets cultured in the presence of high glucose (16.7 mM),
whereas a slight stimulation occurred at 5.5 mM glucose. The selective P2Y6 receptor agonist UDP (200 μM) transiently increased [Ca2+]i and reduced insulin secretion at high glucose, whereas the P2Y2/4 receptor agonist UTP and adenosine receptor agonist NECA were inactive. [Ca2+]i transients induced by 2-MeSADP and UDP were antagonized by suramin (100 μM), U73122 (2 μM, PLC inhibitor), and 2-APB (10
or 30 μM, IP3 receptor antagonist), but neither by staurosporine (1 μM, PKC inhibitor) nor depletion of extracellular Ca2+. The effect of 2-MeSADP on [Ca2+]i was also significantly inhibited by MRS2500, a P2Y1 receptor antagonist. These results suggested that P2Y1 and P2Y6 receptor subtypes are involved in Ca2+ mobilization from intracellular stores and insulin release in mouse islets. In beta-TC6 cells, ATP, ADP, 2-MeSADP, and UDP
transiently elevated [Ca2+]i and slightly decreased insulin secretion at normal glucose, while UTP and NECA were inactive. RT-PCR analysis detected mRNAs
of P2Y1 and P2Y6, but not P2Y2 and P2Y4 receptors. 相似文献
8.
Bjaelde RG Arnadottir SS Leipziger J Praetorius HA 《The Journal of membrane biology》2011,244(1):43-53
Translocation of vesicles within the cytoplasm is essential to normal cell function. The vesicles are typically transported
along the microtubules to their destination. The aim of this study was to characterize the vesicular movement in resting and
stimulated renal epithelial cells. MDCK cells loaded with either quinacrine or acridine orange, dyes taken up by acidic vesicles,
were observed at 37°C in semiopen perfusion chambers. Time-lapse series were analyzed by Imaris software. Our data revealed
vigorous movement of stained vesicles in resting MDCK cells. These movements seem to require intact microtubules because nocodazole
leads to a considerable reduction of the vesicular movements. Interestingly, we found that extracellular ATP caused the vesicular
movement to cease. This observation was obvious in time lapse. Similarly, other stimuli known to increase the intracellular
Ca2+ concentration ([Ca2+]i) in MDCK cells (increment in the fluid flow rate or arginine vasopressin) also reduced the vesicular movement. These findings
were quantified by analysis of single vesicular movement patterns. In this way, ATP was found to reduce the lateral displacement
of the total population of vesicles by 40%. Because all these perturbations increase [Ca2+]i, we speculated that this increase in [Ca2+]i was responsible for the vesicle arrest. Therefore, we tested the effect of the Ca2+ ionophore, ionomycin (1 μM), which in the presence of extracellular Ca2+ resulted in a considerable and sustained reduction of vesicular movement amounting to a 58% decrease in average lateral vesicular
displacement. Our data suggest that vesicles transported on microtubules are paused when subjected to high intracellular Ca2+ concentrations. This may provide an additional explanation for the cytotoxic effect of high [Ca2+]i. 相似文献
9.
The effect of ANG II on pHi, [Ca2+]i and cell volume was investigated in T84 cells, a cell line originated from colon epithelium, using the probes BCECF-AM, Fluo
4-AM and acridine orange, respectively. The recovery rate of pHi via the Na+/H+ exchanger was examined in the first 2 min following the acidification of pHi with a NH4Cl pulse. In the control situation, the pHi recovery rate was 0.118 ± 0.001 (n = 52) pH units/min and ANG II (10−12 M or 10−9 M) increased this value (by 106% or 32%, respectively) but ANG II (10−7 M) decreased it to 47%. The control [Ca2+]i was 99 ± 4 (n = 45) nM and ANG II increased this value in a dose-dependent manner. The ANG II effects on cell volume were minor and late
and should not interfere in the measurements of pHi recovery and [Ca2+]i. To document the signaling pathways in the hormonal effects we used: Staurosporine (a PKC inhibitor), W13 (a calcium-dependent
calmodulin antagonist), H89 (a PKA inhibitor) or Econazole (an inhibitor of cytochrome P450 epoxygenase). Our results indicate
that the biphasic effect of ANG II on Na+/H+ exchanger is a cAMP-independent mechanism and is the result of: 1) stimulation of the exchanger by PKC signaling pathway
activation (at 10−12 – 10−7 M ANG II) and by increases of [Ca2+]i in the lower range (at 10−12 M ANG II) and 2) inhibition of the exchanger at high [Ca2+]i levels (at 10−9 – 10−7 M ANG II) through cytochrome P450 epoxygenase-dependent metabolites of the arachidonic acid signaling pathway. 相似文献
10.
We investigated the contribution of L-, N- and P/Q-type Ca2+ channels to the [Ca2+]i changes, evoked by kainate, in the cell bodies of hippocampal neurons, using a pharmacological approach and Ca2+ imaging. Selective Ca2+ channel blockers, namely nitrendipine, ω-Conotoxin GVIA (ω-GVIA) and ω-Agatoxin IVA (ω-AgaIVA) were used. The [Ca2+]i changes evoked by kainate presented a high variability, and were abolished by NBQX, a AMPA/kainate receptor antagonist, but
the N-methyl-d-aspartate (NMDA) receptor antagonist, D-AP5, was without effect. Each Ca2+ channel blocker caused differential inhibitory effects on [Ca2+]i responses evoked by kainate. We grouped the neurons for each blocker in three subpopulations: (1) neurons with responses
below 60% of the control; (2) neurons with responses between 60% and 90% of the control, and (3) neurons with responses above
90% of the control. The inhibition caused by nitrendipine was higher than the inhibition caused by ω-GVIA or ω-AgaIVA. Thus,
in the presence of nitrendipine, the percentage of cells with responses below 60% of the control was 41%, whereas in the case
of ω-GVIA or ω-AgaIVA the values were 9 or 17%, respectively. The results indicate that hippocampal neurons differ in what
concerns their L-, N- and P/Q- type Ca2+ channels activated by stimulation of the AMPA/kainate receptors.
Special issue article in honor of Dr. Ricardo Tapia. 相似文献
11.
E. A. Turovskii M. V. Konakov A. V. Berezhnov V. P. Zinchenko G. E. Bronnikov L. P. Dolgacheva 《Cell and Tissue Biology》2011,5(5):511-519
The thermogenic capability of brown adipose tissue is controlled by noradrenaline. By interacting with α1- and β-adrenoreceptors
of adipocytes, noradrenaline (NA) increases the intracellular concentration of Ca2+ ([Ca2+]i) and cAMP. The changes in [Ca2+]i under the action of NA and selective agonists of α1- and β-adrenoreceptors, i.e., cirazoline and isoproterenol (IP), are
recorded on individual cells of the primary culture of adipocytes during the day in vitro (DIV) 1, DIV 3, and DIV 6. The change
in [Ca2+]i under the effect of IP as compared to the response to cirazoline in cells of DIV 1 is characterized by a higher amplitude
and shorter duration of impulses in the entire diapason of the used physiological concentrations. After DIV 3, these differences
are insignificant and, after DIV 6, the differences in kinetics are nearly absent. For all three agonists, the kinetics of
the [Ca2+]i change in the proliferating and differentiated cells is significantly different; i.e., the response amplitude increases with
the age of the culture and the duration of transitory response decreases, while sensitivity to agonists of adrenoreceptors
increases. It can be seen from the rise in [Ca2+]i with an inhibitor of Ca2+-ATPase of the endoplasmic reticulum thapsigargin in calcium-free medium that the source of calcium ions in the endoplasmic
reticulum rises with the growth and development of cells in culture, while the rate at which Ca2+ is pumped out of cells, which characterizes the activity of Ca2+-ATPase of the plasma membrane, increases. 相似文献
12.
SantoDomingo J Fonteriz RI Lobatón CD Montero M Moreno A Alvarez J 《Cellular and molecular neurobiology》2010,30(8):1267-1274
We have investigated the dynamics of the free [Ca2+] inside the secretory granules of neurosecretory PC12 and INS1 cells using a low-Ca2+-affinity aequorin chimera fused to synaptobrevin-2. The steady-state secretory granule [Ca2+] ([Ca2+]SG] was around 20–40 μM in both cell types, about half the values previously found in chromaffin cells. Inhibition of SERCA-type
Ca2+ pumps with thapsigargin largely blocked Ca2+ uptake by the granules in Ca2+-depleted permeabilized cells, and the same effect was obtained when the perfusion medium lacked ATP. Consistently, the SERCA-type
Ca2+ pump inhibitor benzohydroquinone induced a rapid release of Ca2+ from the granules both in intact and permeabilized cells, suggesting that the continuous activity of SERCA-type Ca2+ pumps is essential to maintain the steady-state [Ca2+]SG. Both inositol 1,4,5-trisphosphate (InsP3) and caffeine produced a rapid Ca2+ release from the granules, suggesting the presence of InsP3 and ryanodine receptors in the granules. The response to high-K+ depolarization was different in both cell types, a decrease in [Ca2+]SG in PC12 cells and an increase in [Ca2+]SG in INS1 cells. The difference may rely on the heterogeneous response of different vesicle populations in each cell type.
Finally, increasing the glucose concentration triggered a decrease in [Ca2+]SG in INS1 cells. In conclusion, our data show that the secretory granules of PC12 and INS1 cells take up Ca2+ through SERCA-type Ca2+ pumps and can release it through InsP3 and ryanodine receptors, supporting the hypothesis that secretory granule Ca2+ may be released during cell stimulation and contribute to secretion. 相似文献
13.
Ca2+ release from intracellular stores of pig oocytes was investigated using the Ca2+-sensitive fluorescent dye chlorotetracycline. Oocytes were divided into growing ones and those that completed their growth
using brilliant cresyl blue (BCB) staining. The stained oocytes (BCB “+”) were determined as the ones that completed their
growth, while the stainless ones (BCB “−”) were determined as those in the final stages of growth. In the BCB “+” and BCB
“−” oocytes, prolactin, theophylline, GTP, and GDP cause Ca2+ to exit intracellular stores. In the oocytes that completed their growth, joint action of prolactin and GTP activates additional
release of Ca2+, in which protein kinase C takes part. In growing oocytes, joint action of prolactin and GTP does not lead to additional
release of Ca2+. Joint action of theophylline and GDP in growing oocytes and oocytes that completed the growth stage promotes additional
Ca2+ exit from intracellular stores. This exit is regulated by protein kinase A. The obtained data show that there various routes
of Ca2+ release from intracellular stores in growing and grown pig oocytes. 相似文献
14.
In an earlier study, we showed that mitochondria hyperpolarized after short periods of oxygen-glucose deprivation (OGD), and
this response appeared to be associated with subsequent apoptosis or survival. Here, we demonstrated that hyperpolarization
following short periods of OGD (30 min; 30OGD group) increased the cytosolic Ca2+ ([Ca2+]c) buffering capacity in mitochondria. After graded OGD (0 min (control), 30 min, 120 min), rat cultured hippocampal neurons
were exposed to glutamate, evoking Ca2+influx. The [Ca2+]c level increased sharply, followed by a rapid increase in mitochondrial Ca2+ [Ca2+]m. The increase in the [Ca2+]m level accompanied a reduction in the [Ca2+]c level. After reaching a peak, the [Ca2+]c level decreased more rapidly in the 30OGD group than in the control group. This buffering reaction was pronounced in the
30OGD group, but not in the 120OGD group. The enhanced buffering capacity of the mitochondria may be linked to preconditioning
after short-term ischemic episodes. 相似文献
15.
E. A. Turovsky M. V. Turovskaya A. V. Berezhnov A. V. Tolmacheva N. P. Kaimachnikov L. P. Dolgacheva V. P. Zinchenko E. I. Maevskii V. V. Dynnik 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2012,6(1):35-44
Experiments on cultured mouse adipocytes (9 days in vitro) using fluorescent microscopy have shown that activation of α1- and α2-adrenoceptors by norepinephrine (NE) or α2-adrenoreceptors by L-arginine evokes transient Ca2+ signals, while activation of m3-cholinoreceptors by acetylcholine (ACh) or betaine causes sustained or damped Ca2+ oscillations. The presence in the incubation medium of L-arginine at a low concentration (100–200 μM) is necessary for a vigorous manifestation of these effects, apparently due to
transition of protein kinase G (PKG) and phosphodiesterase V into an active state. In the presence of 1–10 mM L-arginine, the amplitude of the Ca2+ transient response to NE increases and signal duration decreases. ACh and NE upon a sequential addition mutually potentiate
their effects. Using an inhibitory analysis we show that the observed modes are related to the operation of a signaling pathway
with the participation of phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB), endothelial NO synthase (eNOS), cytoplasmic
guanylate cyclase (sGC), protein kinase G (PKG), ADP-ribosyl cyclase (CD38), and the ryanodine receptor (RyR). The formation
of several loops of positive feedbacks (PF) and negative feedbacks (NF) in the signaling system is possible: (i) short PF
loops due to Ca2+-induced Ca2+ release (CICR) from internal stores through the inositol trisphosphate receptor (IP3R) and RyR participating in the transient signal formation; (ii) long PF loop Ca2+ → eNOS → sGC → PKG → CD38 → RyR → Ca2+, which can provide necessary conditions for calcium oscillations arising from short PF loops (CICR); (iii) several NF loops
based on PKG-mediated inhibition of IP3R and activation of Ca2+-ATPases of sarco(endo)plasmic reticulum and of the plasma membrane providing a shutdown of signaling by the pathway phospholipase
C → IP3R → Ca2+ and limiting Ca2+ rise caused by the pathway PI3K → PKB → eNOS → sGC → PKG → CD38 → RyR → Ca2+. Convergence of signaling pathways that involve α1-, α2-, and m3-receptors and then Gβγ-subunits of Gq and Gq proteins acting on PI3Kγ can provide activation of cytoplasmic PKG, which plays a key role in producing transient responses,
in activation of Ca2+ removal and generation of [Ca2+]i oscillations. PKG inhibition (implemented here by KT5823 application) in the presence of any agonist results in rupture of
NF loops controlling Ca2+ transporting systems activity that leads to uncontrolled [Ca2+]i rise and cell death. 相似文献
16.
Schaloske RH Lusche DF Bezares-Roder K Happle K Malchow D Schlatterer C 《BMC cell biology》2005,6(1):13
Background
Stimulation of Dictyostelium discoideum with cAMP evokes an elevation of the cytosolic free Ca2+ concentration ([Ca2+]i). The [Ca2+]i-change is composed of liberation of stored Ca2+ and extracellular Ca2+-entry. The significance of the [Ca2+]i-transient for chemotaxis is under debate. Abolition of chemotactic orientation and migration by Ca2+-buffers in the cytosol indicates that a [Ca2+]i-increase is required for chemotaxis. Yet, the iplA - mutant disrupted in a gene bearing similarity to IP3-receptors of higher eukaryotes aggregates despite the absence of a cAMP-induced [Ca2+]i-transient which favours the view that [Ca2+]i-changes are insignificant for chemotaxis. 相似文献17.
Liu J Wang F Huang C Long LH Wu WN Cai F Wang JH Ma LQ Chen JG 《Cellular and molecular neurobiology》2009,29(3):317-328
Recent evidences indicate the existence of an atypical D1 dopamine receptor other than traditional D1 dopamine receptor in the brain that mediates PI hydrolysis via activation of phospholipase Cβ (PLCβ). To further understand the basic physiological function of this receptor in brain, the effects of a selective phosphoinositide
(PI)-linked D1 dopamine receptor agonist SKF83959 on cytosolic free calcium concentration ([Ca2+]i) in cultured rat prefrontal cortical astrocytes were investigated by calcium imaging. The results indicated that SKF83959
caused a transient dose-dependent increase in [Ca2+]i. Application of D1 receptor, but not D2, α1 adrenergic, 5-HT receptor, or cholinergic antagonist prevented SKF83959-induced [Ca2+]i rise, indicating that activation of the D1 dopamine receptor was essential for this response. Increase in [Ca2+]i was a two-step process characterized by an initial increase in [Ca2+]i mediated by release from intracellular stores, supplemented by influx through voltage-gated calcium channels, receptor-operated
calcium channels, and capacitative Ca2+ entry. Furthermore, SKF83959-stimulated increase in [Ca2+]i was abolished following treatment with a PLC inhibitor. Overall, these results suggested that activation of D1 receptor by SKF83959 mediates a dose-dependent mobilization of [Ca2+]i via the PLC signaling pathway in cultured rat prefrontal cortical astrocytes. 相似文献
18.
Kirti Dhingra Petra Fousková Goran Angelovski Martin E. Maier Nikos K. Logothetis Éva Tóth 《Journal of biological inorganic chemistry》2008,13(1):35-46
Two new bismacrocyclic Gd3+ chelates containing a specific Ca2+ binding site were synthesized as potential MRI contrast agents for the detection of Ca2+ concentration changes at the millimolar level in the extracellular space. In the ligands, the Ca2+-sensitive BAPTA-bisamide central part is separated from the DO3A macrocycles either by an ethylene (L1) or by a propylene (L2) unit [H4BAPTA is 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid; H3DO3A is 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid]. The sensitivity of the Gd3+ complexes towards Ca2+ and Mg2+ was studied by 1H relaxometric titrations. A maximum relaxivity increase of 15 and 10% was observed upon Ca2+ binding to Gd2L1 and Gd2L2, respectively, with a distinct selectivity of Gd2L1 towards Ca2+ compared with Mg2+. For Ca2+ binding, association constants of log K = 1.9 (Gd2L1) and log K = 2.7 (Gd2L2) were determined by relaxometry. Luminescence lifetime measurements and UV–vis spectrophotometry on the corresponding Eu3+ analogues proved that the complexes exist in the form of monohydrated and nonhydrated species; Ca2+ binding in the central part of the ligand induces the formation of the monohydrated state. The increasing hydration number
accounts for the relaxivity increase observed on Ca2+ addition. A 1H nuclear magnetic relaxation dispersion and 17O NMR study on Gd2L1 in the absence and in the presence of Ca2+ was performed to assess the microscopic parameters influencing relaxivity. On Ca2+ binding, the water exchange is slightly accelerated, which is likely related to the increased steric demand of the central
part leading to a destabilization of the Ln–water binding interaction.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
Gang Tang Yi Shen Pan Gao Shuang-Shuang Song Liang-Yi Si 《In vitro cellular & developmental biology. Animal》2018,54(3):250-256
Cardiac hypertrophy plays a major role in heart failure and is related to patient morbidity and mortality. Calcium overloading is a main risk for cardiac hypertrophy, and Na+/K+-ATPase (NKA) has been found that it could not only regulate intracellular Na+ levels but also control the intracellular Ca2+ ([Ca2+]i) level through Na+/Ca2+-exchanger (NCX). Recent studies have reported that klotho could affect [Ca2+]i level. In this study, we aimed at exploring the role of klotho in improving isoproterenol-induced hypertrophic response of H9C2 cells. The H9C2 cells were randomly divided into control and isoproterenol (ISO) (10 μM) groups. Klotho protein (10 μg/ml) or NKAα2 siRNA was used to determine the changes in isoproterenol-induced hypertrophic response. The alterations of [Ca2+]i level were measured by spectrofluorometry. Our results showed that H9C2 cells which were treated with isoproterenol presented a higher level of [Ca2+]i and hypertrophic gene expression at 24 and 48 h compared with the control group. Moreover, the expressions of NKAα1 and NKAα2 were both increased in control and ISO groups after treating with klotho protein; meanwhile, the NKA activity was increased and NCX activity was decreased after treatment. Consistently, the [Ca2+]i level and hypertrophic gene expression were decreased in ISO group after klotho protein treatment. However, these effects were both prevented by transfecting with NKAα2 siRNA. In conclusion, these findings demonstrated that klotho inhibits isoproterenol-induced hypertrophic response in H9C2 cells by activating NKA and inhibiting the reverse mode of NCX and this effect may be associated with the upregulation of NKAα2 expression. 相似文献
20.
Intracellular calcium ([Ca2+]i) plays a pivotal role in neuronal ischemia. The aim of the present study was to investigate the routes of Ca2+ entry during non-excitotoxic oxygen and glucose deprivation (OGD) in acutely dissociated rat CA1 neurons. During OGD the fluo-3/fura red ratio reflecting [Ca2+]i increased rapidly and irreversibly. [Ca2+]i increased to the same degree in Ca2+ depleted medium, and also when both the ryanodine receptors (RyR) and the inositol 1,4,5-trisphosphate (IP3) receptors were blocked. When the endoplasmic reticulum (ER) Ca2+ stores were emptied with thapsigargin no increase in [Ca2+]i was observed independent of extracellular Ca2+. The OGD induced Ca2+ deregulation in isolated CA1 neurons is not prevented by removing Ca2+, or by blocking the IP3– or RyR receptors. However, when SERCA was blocked, no increase in [Ca2+]i was observed suggesting that SERCA dysfunction represents an important mechanism for ischemic Ca2+ overload. 相似文献