scholarly journals Recovery from hypoxia-induced internalization of cardiac Na+ /H + exchanger 1 requires an adequate intracellular store of antioxidants

2018 ◽  
Vol 234 (4) ◽  
pp. 4681-4694
Author(s):  
Gül Şimşek ◽  
Richard D. Vaughan-Jones ◽  
Pawel Swietach ◽  
H. Burak Kandilci
Keyword(s):  
Intracellular Store

La3+ and pH sensitivity of Ca2+ entry and intracellular store filling in gastric parietal cells

1995 ◽  
Vol 269 (5) ◽  
pp. G770-G778 ◽  
Author(s):  
P. A. Negulescu ◽  
T. E. Machen
Keyword(s):  
Positive Feedback ◽  
Low Ph ◽  
Parietal Cells ◽  
Additional Increase ◽  
Cholinergic Agonist ◽  
Intracellular Store ◽  
Entry Pathway ◽  
Signaling Function ◽  
Previously Treated ◽  
Gastric Parietal Cells

The fluorescent Ca2+ indicator fura 2 was used to measure cytosolic free [Ca2+] ([Ca2+]i) in order to obtain information about relative rates of Ca2+ influx into parietal cells during treatment with carbachol (a cholinergic agonist) or thapsigargin (TG, a Ca(2+)-mobilizing agent) or during reloading of the internal Ca2+ stores. In Ca(2+)-containing solutions, carbachol-, TG-, and reloading-stimulated Ca2+ entry exhibited nearly identical sensitivity to La3+ [inhibition constant (Ki) approximately 10 microM] or low pH (pKi approximately 7.0). In experiments in which carbachol and TG were used, there was no additional increase in [Ca2+]i when TG was added to carbachol-treated cells or when carbachol was added to cells previously treated with TG. Thus it is likely that a single Ca2+ entry pathway serves a signaling function as well as a role in refilling the Ca2+ store during reloading. Because the Ca2+ pathway is exquisitely sensitive to pH and serosal pH increases during stimulant-induced H+ secretion (which is activated by increases in [Ca2+]i), this mechanism will exert positive feedback on parietal cells in the intact stomach. When parietal cells were pretreated with carbachol in Ca(2+)-free solutions, reloading was independent of pH and La3+, suggesting that Ca(2+)-containing solutions should be used to determine the properties of the influx pathway.

Sequestration of glutamate-induced Ca2+ loads by mitochondria in cultured rat hippocampal neurons

1996 ◽  
Vol 76 (3) ◽  
pp. 1611-1621 ◽  
Author(s):  
G. J. Wang ◽  
S. A. Thayer
Keyword(s):  
Hippocampal Neurons ◽  
Cultured Cells ◽  
High Capacity ◽  
Poor Correlation ◽  
Plateau Phase ◽  
Similar Treatment ◽  
Intracellular Store ◽  
Glutamate Concentration ◽  
The Media ◽  
Maximal Rise

1. Buffering of glutamate-induced Ca2+ loads in single rat hippocampal neurons grown in primary culture was studied with ratiometric fluorescent Ca2+ indicators. The hypothesis that mitochondria buffer the large Ca2+ loads elicited by glutamate was tested. 2. The relationship between glutamate concentration and the resulting increase in the free intracellular Ca2+ concentration ([Ca2+]i) reached an asymptote at 30 microM glutamate. This apparent ceiling was not a result of saturation of the Ca2+ indicator, because these results were obtained with the low-affinity (dissociation constant = 7 microM) Ca2+ indicator coumarin benzothiazole. 3. Five minutes of exposure to glutamate elicited concentration-dependent neuronal death detected 20-24 h later by the release of the cytosolic enzyme lactate dehydrogenase into the media. Maximal neurotoxicity was elicited at glutamate concentrations > or = 300 microM. The discrepancy between the glutamate concentration required to evoke a maximal rise in [Ca2+]i and the higher concentration necessary elicit maximal Ca(2+)-triggered cell death suggests that large neurotoxic Ca2+ loads are in part removed to a noncytoplasmic pool. 4. Treatment of hippocampal neurons with the protonophore carbonyl cyanide p-(trifluoro-methoxy) phenylhydrazone (FCCP; 1 microM, 5 min) greatly increased the amplitude of glutamate-induced [Ca2+]i transients, although it had little effect on basal [Ca2+]i. The effect of FCCP was more pronounced on responses elicited by stimuli that produced large Ca2+ loads. Similar results were obtained by inhibition of electron transport with antimycin A1. Neither agent, under the conditions described here, significantly depressed cellular ATP levels as indicated by luciferase-based ATP measurements, consistent with the robust anaerobic metabolism of cultured cells. Thus inhibition of mitochondrial function disrupted the buffering of glutamate-induced Ca2+ loads in a manner that was not related to changes in ATP. 5. Removal of extracellular Na+ for 20 min before exposure to N-methyl-D-aspartate (NMDA) (200 microM, 3 min), presumably reducing intracellular Na+, evoked a prolonged plateau phase in the recovery of the [Ca2+]i transient that resembled the mitochondrion-mediated [Ca2+]i plateau previously observed in sensory neurons. Return of extracellular Na+ immediately after exposure to NMDA increased the height and shortened the duration of the plateau phase. Thus manipulation of extracellular Na+ altered the plateau in a manner consistent with plateau height being modulated by intracellular Na+ levels. 6. In neurons depleted of Na+ and challenged with NMDA, a plateau resulted; during the plateau, application of FCCP in the absence of extracellular Ca2+ produced a large increase in [Ca2+]i. In contrast, similar treatment of cells that were not depleted of Na+ failed to increase [Ca2+]i. Thus Na+ depletion traps Ca2+ within an FCCP-sensitive intracellular store. 7. Glutamate-induced Ca2+ loads are sequestered by an intracellular store that had a low affinity and a high capacity for Ca2+, was released by FCCP, was sensitive to antimycin A1, and was modulated by intracellular Na+ levels. We conclude that mitochondria sequester glutamate-induced Ca2+ loads and suggest that Ca2+ entry into mitochondria may account for the poor correlation between glutamate-induced neurotoxicity and glutamate-induced changes in [Ca2+]i.

Ca transport by plasma membrane and intracellular stores of gastric cells

1993 ◽  
Vol 264 (4) ◽  
pp. C843-C851 ◽  
Author(s):  
P. A. Negulescu ◽  
T. E. Machen
Keyword(s):  
Plasma Membrane ◽  
Intracellular Pool ◽  
Intracellular Store ◽  
Membrane Pump ◽  
Gastric Cells ◽  
Resting Cell ◽  
Ca Transport ◽  
Pump Activity ◽  
Basolateral Plasma Membrane ◽  
Gastric Parietal Cells

The relative Ca transport activities (i.e., of both pumps and leaks) of carbachol-releasable intracellular stores and the basolateral plasma membrane of gastric parietal cells were studied using digital image processing of fura-2 fluorescence. Cells were treated with either carbachol (a cholinergic agonist) or thapsigargin (an inhibitor of microsomal Ca-adenosinetriphosphatase) or a combination of the two. Ca-free solutions were used to selectively investigate intracellular store release and plasma membrane pump activity, whereas Ca-containing solutions were used to investigate Ca influx and refilling of the intracellular pool. In the resting cell depletion of the intracellular pool in Ca-free solutions was 15-fold faster than control in the presence of thapsigargin, indicating the efficient (> 90%) recycling of leaked Ca by the store Ca pump. Stimulation with carbachol increased the rate of pool depletion by 70-fold, and this Ca flux out of the internal store was ten times larger than the flux across the plasma membrane. Thus the internal store has ten times greater fluxes (both leaks and pumps) than the plasma membrane during resting and stimulated conditions. After carbachol removal (i.e., reloading) the permeability of the internal store decreases, whereas increased influx across the plasma membrane persists until the store is refilled. Cytoplasmic Ca does not increase during refilling because the intracellular store pump operates eightfold faster than the plasma membrane pump, effectively sequestering Ca as quickly as it enters the cell.

Silver Ion Triggers Ca2+ Release from Intracellular Store Sites in Saponin-Treated HL-60 Cells

1991 ◽  
Vol 197 (2) ◽  
pp. 201-207 ◽  
Author(s):  
F. Taguchi ◽  
E. Suematsu ◽  
J. Nishimura ◽  
H. Nawata
Keyword(s):  
Silver Ion ◽  
Intracellular Store

Roles of Ca2+ and protein kinase C in the excitatory response to serotonin in embryonic molluscan ciliary cells

2006 ◽  
Vol 84 (6) ◽  
pp. 635-646 ◽  
Author(s):  
Shandra A. Doran ◽  
Jeffrey I. Goldberg
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Calcium Influx ◽  
Beat Frequency ◽  
Ciliary Beat Frequency ◽  
Excitatory Response ◽  
Helisoma Trivolvis ◽  
Intracellular Store ◽  
Calphostin C ◽  
Kinase C

We examined the roles of Ca2+ and protein kinase C (PKC) in the cilio-excitatory response to serotonin in pedal ciliary cells from Helisoma trivolvis embryos. Serotonin (5-hydroxytryptamine; 5-HT; 100 µmol/L) induced an increase in ciliary beat frequency (CBF) was abolished by microinjected BAPTA (50 mmol/L), but was only partially inhibited by the phospholipase C inhibitor U-73122 (10 µmol/L). The diacylglycerol analogs 1-oleoyl-2-acetyl-sn-glycerol (100 µmol/L) and 1,2-dioctanoyl-sn-glycerol (100 µmol/L) caused increases in [Ca2+]i that were smaller than those induced by serotonin. In the absence of extracellular Ca2+, 1,2-dioctanoyl-sn-glycerol (100 µmol/L) failed to elicit an increase in both CBF and [Ca2+]i. In contrast, the serotonin-induced increase in CBF persisted in the absence of extracellular Ca2+, although the increase in [Ca2+]i was abolished. PKC inhibitors bisindolylmaleimide (10 and 100 nmol/L) and calphostin C (10 nmol/L) partially inhibited the serotonin-induced increase in CBF, but didn’t affect the serotonin-induced change in [Ca2+]i. These findings suggest that an intracellular store-dependent increase in [Ca2+]i mediates the cilio-excitatory response to serotonin. Furthermore, although PKC is able to cause an increase in [Ca2+]i through calcium influx, it contributes to the cilio-excitatory response to 5-HT through a different mechanism.

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