共查询到20条相似文献,搜索用时 31 毫秒
1.
Michalina Kosiorek Paulina Podszywalow-Bartnicka Ludmila Zylinska Krzysztof Zablocki Slawomir Pikula 《Biochemical and biophysical research communications》2011,411(2):89
PMCA1–4 isoforms have been recently recognised as regulators of various signalling pathways in mammalian cells. PMCAs were found to interact with calcineurin A in an isoform specific manner. In this study we focus on the interaction of calcineurin A with PMCA4 and its effect on catecholamine secretion in PC12 cells with reduced PMCA2 or PMCA3 content. Reduction of synthesis of PMCA2 or PMCA3 led to upregulation of PMCA4 manifested by preferential interaction of PMCA4 with calcineurin A. On the other hand, we observed a significant reduction of dopamine secretion, which did not correspond with an increased [Ca2+]c. This result indicates that the interaction of PMCA4 with calcineurin A plays a regulatory role in the signalling during catecholamine secretion. 相似文献
2.
The receptor‐evoked Ca2+ signal is sensed and translated by mitochondria. Physiological cytoplasmic Ca2+ ([Ca2+]c) oscillations result in mitochondrial Ca2+ ([Ca2+]m) oscillations, while large and sustained [Ca2+]c increase results in a pathologic increase in basal [Ca2+]m and in Ca2+ accumulation. The physiological [Ca2+]m signal regulates [Ca2+]c and stimulates oxidative metabolism, while excess Ca2+ accumulation causes cell stress leading to cell death. [Ca2+]m is determined by Ca2+ uptake mediated by the mitochondria Ca2+ uniporter (MCU) channel and by Na+‐ and H+‐coupled Ca2+ extrusion 1 . 相似文献
3.
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
4.
Dehydroepiandrosterone (DHEA) is a putative anti-stress agent and stress is associated with the secretion of catecholamine from the adrenal gland, but the effects of DHEA on catecholamine secretion are not fully understood. Using bovine chromaffin cells, we found that DHEA inhibited catecholamine secretion and cytosolic Ca2+ ([Ca2+]i) rise coupled with nicotinic acetylcholine receptor (nAChR) without exerting an effect on3H-nicotine binding. In the case of high K+ stimulation, DHEA effectively suppressed secretion without affecting [Ca2+]1 rise. Trifluoperazine (TFP), a calmodulin inhibitor, was capable of counteracting the inhibition of DHEA on high K+-induced secretions. In permeabilized cells, DHEA suppressed the Ca2+-induced secretion. These results suggest that DHEA (a) acts as a channel blocker that suppresses Ca2+ influx and subsequent secretions associated with nAChR, or (b) affects the intracellular secretion machinery to suppress high K+-induced secretions without affecting the high K+-induced [Ca2+]i rise. 相似文献
5.
Using roots from Arabidopsis thaliana expressing the recombinant calcium indicator aequorin, we show that NH3 uptake and alkalisation of plant cells act as a stimulus which induces transient elevations of the cytoplasmic free calcium concentration ([Ca2+]c). The magnitudes of these [Ca2+]c elevations are dependent on the concentration of the membrane permeable form, NH3, and hence, particularly dependent on the pH in the external medium. EGTA and La3+ are able to significantly suppress the [Ca2+]c transients showing that Ca2+ influx through the plasma membrane is likely to be involved. Verapamil and nifedipine had no inhibitory effects, which suggests that Ca2+ release from internal stores might not contribute significantly to the NH3‐triggered [Ca2+]c response. Pre‐incubation in l ‐methionine‐dl ‐sulphoximine – an inhibitor of the glutamine synthetase – did not alter the NH3‐induced [Ca2+]c responses at all. These results are consistent with previous studies where NH3‐induced changes of cytoplasmic and vacuolar pH were investigated in maize roots. Furthermore, the similarity between the kinetics of NH3‐driven cellular pH changes demonstrated in previous studies and the [Ca2+]c transients shown here suggests a direct relationship between [Ca2+]c and cellular alkalisation (cytoplasmic pH and/or vacuolar pH). However, the mechanism behind this possible causal relation remains to be elucidated. 相似文献
6.
Christian Lohr Eric Tucker Lynne A. Oland Leslie P. Tolbert 《Developmental neurobiology》2002,52(2):85-98
Changes in the intracellular Ca2+ concentration ([Ca2+]i) induced by depolarization have been measured in glial cells acutely isolated from antennal lobes of the moth Manduca sexta at different postembryonic developmental stages. Depolarization of the glial cell membrane was elicited by increasing the external K+ concentration from 4 to 25 mM. At midstage 5 and earlier stages, less than 20% of the cells responded to 25 mM K+ (1 min) with a transient increase in [Ca2+]i of approximately 40 nM. One day later, at late stage 5, 68% of the cells responded to 25 mM K+, the amplitude of the [Ca2+]i transients averaging 592 nM. At later stages, all cells responded to 25 mM K+ with [Ca2+]i transients with amplitudes not significantly different from those at late stage 5. In stage 6 glial cells isolated from deafferented antennal lobes, i.e., from antennal lobes chronically deprived of olfactory receptor axons, only 30% of the cells responded with [Ca2+]i transients. The amplitudes of these [Ca2+]i transients averaged 93 nM and were significantly smaller than those in normal stage 6 glial cells. [Ca2+]i transients were greatly reduced in Ca2+‐free, EGTA‐buffered saline, and in the presence of the Ca2+ channel blockers cadmium and verapamil. The results suggest that depolarization of the cell membrane induces Ca2+ influx through voltage‐activated Ca2+ channels into antennal lobe glial cells. The development of the depolarization‐induced Ca2+ transients is rapid between midstage 5 and stage 6, and depends on the presence of afferent axons from the olfactory receptor cells in the antenna. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 85–98, 2002 相似文献
7.
Glucose is a primary stimulator of insulin secretion in pancreatic β-cells. High concentration of glucose has been thought to exert its action solely through its metabolism. In this regard, we have recently reported that glucose also activates a cell-surface glucose-sensing receptor and facilitates its own metabolism. In the present study, we investigated whether glucose activates the glucose-sensing receptor and elicits receptor-mediated rapid actions. In MIN6 cells and isolated mouse β-cells, glucose induced triphasic changes in cytoplasmic Ca2+ concentration ([Ca2+]c); glucose evoked an immediate elevation of [Ca2+]c, which was followed by a decrease in [Ca2+]c, and after a certain lag period it induced large oscillatory elevations of [Ca2+]c. Initial rapid peak and subsequent reduction of [Ca2+]c were independent of glucose metabolism and reproduced by a nonmetabolizable glucose analogue. These signals were also blocked by an inhibitor of T1R3, a subunit of the glucose-sensing receptor, and by deletion of the T1R3 gene. Besides Ca2+, glucose also induced an immediate and sustained elevation of intracellular cAMP ([cAMP]c). The elevation of [cAMP]c was blocked by transduction of the dominant-negative Gs, and deletion of the T1R3 gene. These results indicate that glucose induces rapid changes in [Ca2+]c and [cAMP]c by activating the cell-surface glucose-sensing receptor. Hence, glucose generates rapid intracellular signals by activating the cell-surface receptor. 相似文献
8.
HKC‐8 cells are a human‐derived renal proximal tubular cell line and provide a useful model system for the study of human renal cell function. In this study, we aimed to determine [Ca2+]i signalling mediated by P2 receptor in HKC‐8. Fura‐2 and a ratio imaging method were employed to measure [Ca2+]i in HKC‐8 cells. Our results showed that activation of P2Y receptors by ATP induced a rise in [Ca2+]i that was dependent on an intracellular source of Ca2+, while prolonged activation of P2Y receptors induced a rise in [Ca2+]i that was dependent on intra‐ and extracellular sources of Ca2+. Pharmacological and molecular data in this study suggests that TRPC4 channels mediate Ca2+ entry in coupling to activation of P2Y in HKC‐8 cells. U73221, an inhibitor of PI‐PLC, did not inhibit the initial ATP‐induced response; whereas D609, an inhibitor of PC‐PLC, caused a significant decrease in the initial ATP‐induced response, suggesting that P2Y receptors are coupled to PC‐PLC. Although P2X were present in HKC‐8, The P2X agonist, α,β me‐ATP, failed to cause a rise in [Ca2+]i. However, PPADS at a concentration of 100 µM inhibits the ATP‐induced rise in [Ca2+]i. Our results indicate the presence of functional P2Y receptors in HKC‐8 cells. ATP‐induced [Ca2+]i elevation via P2Y is tightly associated with PC‐PLC and TRP channel. J. Cell. Biochem. 109: 132–139, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
9.
Carole Muller Kamal Yassin Luo-Sheng Li Magnus Palmblad Suad Efendic Per-Olof Berggren Anthony Cerami Michael Brines Claes-G?ran ?stenson 《Molecular medicine (Cambridge, Mass.)》2015,21(1):969-978
Effects of ARA290 on glucose homeostasis were studied in type 2 diabetic Goto-Kakizaki (GK) rats. In GK rats receiving ARA290 daily for up to 4 wks, plasma glucose concentrations were lower after 3 and 4 wks, and hemoglobin A1c (Hb A1c) was reduced by ~20% without changes in whole body and hepatic insulin sensitivity. Glucose-stimulated insulin secretion was increased in islets from ARA290-treated rats. Additionally, in response to glucose, carbachol and KCl, islet cytoplasmic free Ca2+ concentrations, [Ca2+]i, were higher and the frequency of [Ca2+]i oscillations enhanced compared with placebo. ARA290 also improved stimulus–secretion coupling for glucose in GK rat islets, as shown by an improved glucose oxidation rate, ATP production and acutely enhanced glucose-stimulated insulin secretion. ARA290 also exerted an effect distal to the ATP-sensitive potassium (KATP) channel on the insulin exocytotic pathway, since the insulin response was improved following islet depolarization by KCl when KATP channels were kept open by diazoxide. Finally, inhibition of protein kinase A completely abolished effects of ARA290 on insulin secretion. In conclusion, ARA290 improved glucose tolerance without affecting hematocrit in diabetic GK rats. This effect appears to be due to improved β-cell glucose metabolism and [Ca2+]i handling, and thereby enhanced glucose-induced insulin release. 相似文献
10.
Rosa Luisi Elisabetta Panza Vincenzo Barrese Fabio Arturo Iannotti† Davide Viggiano† Agnese Secondo Lorella Maria Teresa Canzoniero Maria Martire‡ Lucio Annunziato Maurizio Taglialatela† 《Journal of neurochemistry》2009,109(1):168-181
In this study, the functional consequences of the pharmacological modulation of the M‐current (IKM) on cytoplasmic Ca2+ intracellular Ca2+concentration ([Ca2+]i) changes and excitatory neurotransmitter release triggered by various stimuli from isolated rat cortical synaptosomes have been investigated. Kv7.2 immunoreactivity was identified in pre‐synaptic elements in cortical slices and isolated glutamatergic cortical synaptosomes. In cerebrocortical synaptosomes exposed to 20 mM [K+]e, the IKM activator retigabine (RT, 10 μM) inhibited [3H]d ‐aspartate ([3H]d ‐Asp) release and caused membrane hyperpolarization; both these effects were prevented by the IKM blocker XE‐991 (20 μM). The IKM activators RT (0.1–30 μM), flupirtine (10 μM) and BMS‐204352 (10 μM) inhibited 20 mM [K+]e‐induced synaptosomal [Ca2+]i increases; XE‐991 (20 μM) abolished RT‐induced inhibition of depolarization‐triggered [Ca2+]i transients. The P/Q‐type voltage‐sensitive Ca2+channel (VSCC) blocker ω‐agatoxin IVA prevented RT‐induced inhibition of depolarization‐induced [Ca2+]i increase and [3H]d ‐Asp release, whereas the N‐type blocker ω‐conotoxin GVIA failed to do so. Finally, 10 μM RT did not modify the increase of [Ca2+]i and the resulting enhancement of [3H]d ‐Asp release induced by [Ca2+]i mobilization from intracellular stores, or by store‐operated Ca2+channel activation. Collectively, the present data reveal that the pharmacological activation of IKM regulates depolarization‐induced [3H]d ‐Asp release from cerebrocortical synaptosomes by selectively controlling the changes of [Ca2+]i occurring through P/Q‐type VSCCs. 相似文献
11.
Maria Teresa Alonso Maria José Barrero Pedro Michelena Estela Carnicero Inmaculada Cuchillo Antonio G. García Javier García-Sancho Mayte Montero Javier Alvarez 《The Journal of cell biology》1999,144(2):241-254
The presence and physiological role of Ca2+-induced Ca2+ release (CICR) in nonmuscle excitable cells has been investigated only indirectly through measurements of cytosolic [Ca2+] ([Ca2+]c). Using targeted aequorin, we have directly monitored [Ca2+] changes inside the ER ([Ca2+]ER) in bovine adrenal chromaffin cells. Ca2+ entry induced by cell depolarization triggered a transient Ca2+ release from the ER that was highly dependent on [Ca2+]ER and sensitized by low concentrations of caffeine. Caffeine-induced Ca2+ release was quantal in nature due to modulation by [Ca2+]ER. Whereas caffeine released essentially all the Ca2+ from the ER, inositol 1,4,5-trisphosphate (InsP3)- producing agonists released only 60–80%. Both InsP3 and caffeine emptied completely the ER in digitonin-permeabilized cells whereas cyclic ADP-ribose had no effect. Ryanodine induced permanent emptying of the Ca2+ stores in a use-dependent manner after activation by caffeine. Fast confocal [Ca2+]c measurements showed that the wave of [Ca2+]c induced by 100-ms depolarizing pulses in voltage-clamped cells was delayed and reduced in intensity in ryanodine-treated cells. Our results indicate that the ER of chromaffin cells behaves mostly as a single homogeneous thapsigargin-sensitive Ca2+ pool that can release Ca2+ both via InsP3 receptors or CICR. 相似文献
12.
To determine whether lipid-secreting cells have cytosolic Ca2+ concentration ([Ca2+]c)-related secretory mechanisms, morphological changes and intracellular calcium dynamics of Harderian glands of guinea pigs stimulated by secretagogs were studied by electron microspy and Fura-2/AM digital image analysis. Control glandular cells contained large lipid vacuoles that were bordered by multi-layered membranes. Rough-surfaced endoplasmic reticulum, mitochondria, and smooth-surfaced endoplasmic reticulum may be involved in lipid vacuole formation. Myoepithelial cells surrounded alveoli. After carbamylcholine (CCh, 10–6, 10–5, and 10–3 M) stimulation, lipid materials within the membranous structures were frequently discharged by an exocytotic mechanism. Conspicuous deformation of glandular cells caused by vigorous contraction of myoepithelial cells was observed in isolated alveoli after 10–6M CCh stimulation, whereas the deformaties of glandular tissues perfused via vessels were small even after 10–3M CCh stimulation. Connective tissue between glandular alveoli inhibited unbridled myoepithelial-cell contraction. Fura-2/AM digital imaging analysis revealed that CCh stimulation caused an increase in [Ca2+]c in isolated alveoli. The morphological reactions and changes in [Ca2+]c were prevented by atropine. When extracellular calcium ions were absent, enhanced extrusion of lipid vacuoles, myoepithelial-cell contraction, and a rise in [Ca2+]c after CCh stimulation were not observed. Nicotine and catecholamines had no effect on the secretion or on the dynamics of [Ca2+]c. It can be concluded that acetylcholine elicits exocytosis in glandular cells and contraction of the myoepithelial cells of Harderian glands, accompanied by an increase in [Ca2+]c. The dynamics of [Ca2+]c of the gland alveoli are mostly dependent on extracellular Ca2+. 相似文献
13.
Daniela Basso Eliana Greco Andrea Padoan Paola Fogar Michele Scorzeto Elisa Fadi Dania Bozzato Stefania Moz Filippo Navaglia Carlo‐Federico Zambon Roberta Seraglia Eugenio De Carlo Anna Valerio Carlo Reggiani Sergio Pedrazzoli Mario Plebani 《Journal of cellular physiology》2011,226(2):456-468
After isolating NT‐S100A8 from pancreatic cancer (PC) tissue of diabetic patients, we verified whether this peptide alters PC cell growth and invasion and/or insulin release and [Ca2+]i oscillations of insulin secreting cells and/or insulin signaling. BxPC3, Capan1, MiaPaCa2, Panc1 (PC cell lines) cell growth, and invasion were assessed in the absence or presence of 50, 200, and 500 nM NT‐S100A8. In NT‐S100A8 stimulated β‐TC6 (insulinoma cell line) culture medium, insulin and [Ca2+] were measured at 2, 3, 5, 10, 15, 30, and 60 min, and [Ca2+]i oscillations were monitored (epifluorescence) for 3 min. Five hundred nanomolars NT‐S100A8 stimulated BxPC3 cell growth only and dose dependently reduced MiaPaCa2 and Panc1 invasion. Five hundred nanomolars NT‐S100A8 induced a rapid insulin release and enhanced β‐TC6 [Ca2+]i oscillations after both one (F = 6.05, P < 0.01) and 2 min (F = 7.42, P < 0.01). In the presence of NT‐S100A8, [Ca2+] in β‐TC6 culture medium significantly decreased with respect to control cells (F = 6.3, P < 0.01). NT‐S100A8 did not counteract insulin induced phosphorylation of the insulin receptor, Akt and IκB‐α, but it independently activated Akt and NF‐κB signaling in PC cells. In conclusion, NT‐S100A8 exerts a mild effect on PC cell growth, while it reduces PC cell invasion, possibly by Akt and NF‐κB signaling, NT‐S100A8 enhances [Ca2+]i oscillations and insulin release, probably by inducing Ca2+ influx from the extracellular space, but it does not interfere with insulin signaling. J. Cell. Physiol. 226: 456–468, 2011. © 2010 Wiley‐Liss, Inc. 相似文献
14.
Patricia Santofimia-Castaño Deborah Clea Ruy Ginés M. Salido Antonio González 《Journal of physiology and biochemistry》2013,69(4):897-908
In the present work, we have evaluated the effect of an acute addition of melatonin on cholecystokinin octapeptide (CCK-8)-evoked Ca2+ signals and amylase secretion in mouse pancreatic acinar cells. For this purpose, freshly isolated mouse pancreatic acinar cells were loaded with fura-2 to study intracellular free Ca2+ concentration ([Ca2+]c). Amylase release and cell viability were studied employing colorimetric methods. Our results show that CCK-8 evoked a biphasic effect on amylase secretion, finding a maximum at a concentration of 0.1 nM and a reduction of secretion at higher concentrations. Pre-incubation of cells with melatonin (1 μM–1 mM) significantly attenuated enzyme secretion in response to high concentrations of CCK-8. Stimulation of cells with 1 nM CCK-8 led to a transient increase in [Ca2+]c, followed by a decrease towards a constant level. In the presence of 1 mM melatonin, stimulation of cells with CCK-8 resulted in a smaller [Ca2+]c peak response, a faster rate of decay of [Ca2+]c and lower values for the steady state of [Ca2+]c, compared with the effect of CCK-8 alone. Melatonin also reduced the oscillatory pattern of Ca2+ mobilization evoked by a physiological concentration of CCK-8 (20 pM), and completely inhibited Ca2+ mobilization induced by 10 pM CCK-8. On the other hand, Ca2+ entry from the extracellular space was not affected in the presence of melatonin. Finally, melatonin alone did not change cell viability. We conclude that melatonin, at concentrations higher than those found in blood, might regulate exocrine pancreatic function via modulation of Ca2+ signals. 相似文献
15.
The sensing of extracellular Ca2+ concentration ([Ca2+]o) and modulation of cellular processes associated with acute or sustained changes in [Ca2+]o are cell-type specific and mediated by the calcium sensing receptor (CaR). [Ca2+]o signalling requires protein kinase C (PKC), but the identity and role of PKC isoforms in CaR-mediated responses remain unclear. Here we show that high [Ca2+]o activated PKC-α and PKC-ε in parathyroid cells and in human embryonic kidney (HEK293) cells overexpressing the CaR (HEK-CaR) and that this response correlated with the CaR-dependent activation of mitogen-activated protein kinases ERK1/2. Activation of ERK1/2 by acute high [Ca2+]o required influx of Ca2+through Ni2+-sensitive Ca2+channels and phosphatidylinositol-dependent phospholipase C-β activity. Inhibition of PKC by co-expression of dominant-negative (DN) mutants of PKC-α or -ε with the CaR attenuated sustained ERK1/2 activation. Overexpression of a PKC phosphorylation site (T888A) mutant CaR in HEK293 cells showed that this site was important for ERK1/2 activation at high [Ca2+]o. Activation of ERK1/2 by high [Ca2+]o was not necessary for the [Ca2+]o-regulated secretion of parathyroid hormone (PTH) in dispersed bovine parathyroid cells. These data suggest that the CaR-mediated [Ca2+]o signal leading to regulated PTH secretion that requires diacylglycerol-responsive PKC isoforms is not mediated via the ERK pathway. 相似文献
16.
The effect of hydrogen peroxide (H2O2) on cytosolic free calcium concentration ([Ca2+]c) as well as its effect on glutamate secretion in rat hippocampal astrocytes have been the aim of the present research. Our results show that 100 μM H2O2 induces an increase in [Ca2+]c, that remains at an elevated level while the oxidant is present in the perfusion medium, due to its release from intracellular stores as it was observed in the absence of extracellular Ca2+, followed by a significant increase in glutamate secretion. Ca2+-mobilization in response to the oxidant could only be reduced by thapsigargin plus FCCP, indicating that the Ca2+-mobilizable pool by H2O2 includes both endoplasmic reticulum and mitochondria. We conclude that ROS in hippocampal astrocytes might contribute to an elevation of resting [Ca2+]c which, in turn, could lead to a maintained secretion of the excitatory neurotransmitter glutamate, which has been considered a situation potentially leading to neurotoxicity in the hippocampus. 相似文献
17.
Camilla Rozanski Michelle Belton Frank S. Prato Jeffrey J.L. Carson 《Bioelectromagnetics》2009,30(3):213-221
This study investigated whether glutathione depletion affected the sensitivity of HL‐60 cells to static magnetic fields. The effect of Diethylmaleate (DEM) on static magnetic field induced changes in cytosolic free calcium concentration ([Ca2+]c) was examined. Cells were loaded with a fluorescent dye and exposed to a uniform static magnetic field at a strength of 0 mT (sham) or 100 mT. [Ca2+]c was monitored during field and sham exposure using a ratiometric fluorescence spectroscopy system. Cells were activated by the addition of ATP. Metrics extracted from the [Ca2+]c time series included: average [Ca2+]c during the Pre‐Field and Field Conditions, peak [Ca2+]c following ATP activation and the full width at half maximum (FWHM) of the peak ATP response. Comparison of each calcium metric between the sham and 100 mT experiments revealed the following results: average [Ca2+]c measured during the Field condition was 53 ± 2 nM and 58 ± 2 nM for sham and 100 mT groups, respectively. Average FWHM was 51 ± 3 s and 54 ± 3 s for sham and 100 mT groups, respectively. An effect of experimental order on the peak [Ca2+]c response to ATP in sham/sham experiments complicated the statistical analysis and did not allow pooling of the first and second order experiments. No statistically significant difference between the sham and 100 mT groups was observed for any of the calcium metrics. These data suggested that manipulation of free radical buffering capacity in HL‐60 cells did not affect the sensitivity of the cells to a 100 mT static magnetic field. Bioelectromagnetics 30:213–221, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
18.
Selective Changes in Cell Bodies and Growth Cones of Nerve Growth Factor-Differentiated PC12 Cells Induced by Chemical Hypoxia 总被引:2,自引:1,他引:1
Abstract: Cytosolic free Ca2+ concentration ([Ca2+]i) was measured in differentiated PC12 cells to test whether chemical hypoxia selectively alters intracellular Ca2+ in growth cones and cell bodies. Hypoxia increased [Ca2+]i and exaggerated its response to K+ depolarization in both parts of the cells. [Ca2+]i in the cell bodies was greater than that in the growth cones under resting conditions and in response to K+ or hypoxia. Ca2+-channel blockers selectively altered these responses. The L-channel blocker nifedipine reduced [Ca2+]i following K+ depolarization by 67% in the cell bodies but only 25% in the growth cones. In contrast, the N-channel blocker ω-conotoxin GVIA (ω-CgTX) diminished K+-induced changes in [Ca2+]i only in the growth cones. During hypoxia, nifedipine was more effective in the cell bodies than in the growth cones. During hypoxia, ω-CgTX diminished K+-induced changes by 50–75% in both parts of the cell, but only immediately after depolarization. The combination of nifedipine and ω-CgTX diminished the [Ca2+]i response to K+ with or without hypoxia by >90% in the cell body and 70% in the growth cones. Thus, the increased Ca2+ entry with K+ during hypoxia is primarily through L channels in the cell bodies, whereas in growth cones influx through L and N channels is about equal. The results show that chemical hypoxia selectively alters Ca2+ regulation in the growth cone and cell body of the same cell. 相似文献
19.
Changes in cytosolic free Ca2+ concentration ([Ca2+]c) play a crucial role in the control of insulin secretion from the electrically excitable pancreatic β-cell. Secretion is controlled by the finely tuned balance between Ca2+ influx (mainly through voltage-dependent Ca2+ channels, but also through voltage-independent Ca2+ channels like store-operated channels) and efflux pathways. Changes in [Ca2+]c directly affect [Ca2+] in various organelles including the endoplasmic reticulum (ER), mitochondria, the Golgi apparatus, secretory granules and lysosomes, as imaged using recombinant targeted probes. Because most of these organelles have specific Ca2+ influx and efflux pathways, they mutually influence free [Ca2+] in the others. In this article, we review the mechanisms of control of [Ca2+] in various compartments and particularly the cytosol, the endoplasmic reticulum ([Ca2+]ER), acidic stores and mitochondrial matrix ([Ca2+]mito), focusing chiefly on the most important physiological stimulus of β-cells, glucose. We also briefly review some alterations of β-cell Ca2+ homeostasis in Type 2 diabetes. 相似文献
20.
The inward K+ channels (IKin) of guard cells are inhibited upon application of abscisic acid (ABA). It has been postulated that IKin inhibition requires an elevation in cytosolic free Ca2+ levels ([Ca2+]c) because: (i) experimental increases in [Ca2+] c can mimic the ABA effect, and; (ii) ABA can trigger an elevation of [Ca2+]c in guard cells. However, not all guard cells respond to ABA with a [Ca2+]c increase, and the magnitude of the increases that do occur is variable. Therefore, an obligate role for Ca2+ in the regulation of downstream effectors of ABA response, such as the IKin channels, remains in question. In this study, we developed a methodology for simultaneous patch clamping and confocal ratiometric
Ca2+ imaging of Vicia faba L. guard-cell protoplasts. This allowed us to directly assess the relationship between ABA-induced changes in [Ca2+]c and IKin inhibition. In the presence of extracellular Ca2+, the extent of [Ca2+]c elevation correlated with the extent of IKin inhibition. However, upon chelation of either extracellular Ca2+, [Ca2+]c, or both, extracellular Ca2+ and [Ca2+]c, [Ca2+]c elevation did not occur in response to ABA yet IKin currents were still strongly inhibited. These data illustrate that Ca2+-independent regulation is involved in ABA-inhibition of stomatal opening processes.
Received: 17 September 1999 / Accepted: 26 October 1999 相似文献