Cerebral anoxia tolerance in turtles: regulation of intracellular calcium and pH

1992 ◽  
Vol 263 (6) ◽  
pp. R1298-R1302
Author(s):  
P. E. Bickler
Keyword(s):  
Intracellular Calcium ◽  
Brain Slices ◽  
Calcium Flux ◽  
Anoxia Tolerance ◽  
Acetoxymethyl Ester ◽  
Fluorescent Indicators ◽  
Cerebral Anoxia ◽  
Atp Production ◽  
Laboratory Rats ◽  
Inhibition Of Glycolysis

To investigate mechanisms of cerebral anoxia tolerance, cerebrocortical intracellular calcium ([Ca2+]i) and pH (pHi) regulation were compared in turtles (Trachemys scripta) and laboratory rats. [Ca2+]i and pHi in living 200 to 300-microns-thick cortical brain slices were measured with the fluorescent indicators fura-2/acetoxymethyl ester (AM) and 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein during exposure to anoxia. Within 5 min, [Ca2+]i increased to > 1,000 nM in rat brain slices exposed to anoxia but [Ca2+]i was normal even after 5 h of anoxia in turtles. ATP levels remained normal in anoxic turtle brain but fell rapidly in rats. During anoxia, pHi fell by 0.25 +/- 0.08 pH units in rats but only 0.10 +/- 0.04 in turtles (P < 0.05). Inhibition of glycolysis in anoxic turtle brain with iodoacetate resulted in large increases in [Ca2+]i but prior exposure of slices to anoxia resulted in greatly attenuated calcium entry. The reduction in calcium flux was greater with increasing exposure to anoxia, suggesting progressive arrest of calcium channel activity. Tolerance of cerebral anoxia in turtles may be related to anaerobic ATP production, arrest of calcium channels, and attenuation of changes in pHi.

Inhibition of brain calcium channels by plasma proteins from anoxic turtles

1993 ◽  
Vol 265 (2) ◽  
pp. R277-R281 ◽  
Author(s):  
P. E. Bickler ◽  
S. M. Gallego
Keyword(s):  
Calcium Channels ◽  
Intracellular Calcium ◽  
Sodium Channels ◽  
Plasma Proteins ◽  
Brain Slices ◽  
Regulatory Proteins ◽  
Calcium Flux ◽  
Channel Activity ◽  
Cellular Survival ◽  
Calcium Blockade

Recent studies suggest that turtles avoid disturbances in brain ionic regulation during anoxia by reducing the activity of brain calcium and sodium channels. Because glutamate released during anoxia may cause cytotoxic elevations in intracellular calcium, blockade of glutamate-mediated calcium channels may be essential for cellular survival. Elevations in intracellular calcium, measured with the fluorescent dye fura 2, were used to assay glutamate-induced activation of calcium channels in cerebrocortical brain slices from rats and turtles. Fourteen hours of anoxia produced long-lasting reduction in glutamate-mediated calcium flux in the turtle brain. Furthermore, a plasma protein from turtles maintained under anoxic conditions produced blockade of glutamate-mediated calcium flux in cortical brain slices from both turtles and rats. These results suggest that long-lasting modulation of brain calcium channels as well as blockade of calcium channel activity by regulatory proteins may play important roles in reducing transcellular ion fluxes in turtles during anoxia.

scholarly journals Developmental Changes in Intracellular Calcium Regulation in Rat Cerebral Cortex during Hypoxia

1993 ◽  
Vol 13 (5) ◽  
pp. 811-819 ◽  
Author(s):  
Philip E. Bickler ◽  
Steven M. Gallego ◽  
Bonnie M. Hansen
Keyword(s):  
Intracellular Calcium ◽  
Age Groups ◽  
Brain Slices ◽  
Atp Depletion ◽  
Energy Utilization ◽  
Neonatal Rat ◽  
Conservation Of Energy ◽  
Excitatory Neurotransmitter ◽  
Atp Production ◽  
The Central Nervous System

During the first weeks of life, injury to the central nervous system caused by brief periods of oxygen deprivation greatly increases. To investigate possible causes for this change, the effects of hypoxia or application of the excitatory neurotransmitter glutamate on intracellular calcium ([Ca2+]i) and ATP were studied in rat cerebrocortical brain slices. [Ca2+]i was measured fluo-rometrically with the indicator Fura-2. Hypoxia (95% N2/ 5% CO2) or 100 μ M sodium cyanide produced gradual elevations in [Ca2+]i and ATP depletion in slices from rats <2 weeks old, but rapid changes in older rats. After 20 min, [Ca2+]i in adult slices exposed to cyanide was 1,980 ± 310 n M; in day 1–14 animals, it was 796 ± 181 n M (p < 0.05). Combination of cyanide and a glycolytic inhibitor (iodoacetate) rapidly elevated [Ca2+]i and depleted ATP in all age groups. Energy utilization during anoxia, assessed by measuring ATP fall in cyanide/ iodoacetate-treated brain slices, increased with age. Elevations in [Ca2+]i caused by application of 500 μ M glutamate increased 240% from days 1–2 to day 28, but ATP loss caused by glutamate did not change with age. The N-methyl-d-aspartate antagonist MK-801 delayed calcium entry during the initial 5–7 min of hypoxia or cyanide in rats <2 weeks old. We conclude that anaerobic ATP production, conservation of energy by reduced ATP consumption, and reduced sensitivity to glutamate contribute to delaying elevation in [Ca2+]i in neonatal rat brain during hypoxia.

Increased Aggregation and Secretion Responses of Human Platelets when Loaded with the Calcium Fluorescent Probes Quin2 and Fura-2

1987 ◽  
Vol 58 (02) ◽  
pp. 737-743 ◽  
Author(s):  
Frarnçois Lanza ◽  
Alain Beretz ◽  
Martial Kubina ◽  
Jean-Pierre Cazenave
Keyword(s):  
Intracellular Calcium ◽  
Shape Change ◽  
Calcium Ionophore ◽  
Human Platelets ◽  
Arachidonic Acid Metabolism ◽  
Free Calcium ◽  
Membrane Bilayer ◽  
Fluorescent Indicators ◽  
Fura 2 ◽  
Low Concentrations

SummaryIncorporation into human platelets of the calcium fluorescent indicators quin2 or fura-2 at low concentrations used to measure intracellular free calcium leads to the potentiation of the effects of agonists on platelets. This was shown by increased aggregatory and secretory responses of quin2 or fura-2 loaded platelets after stimulation with ADP, PAP and with low concentrations of thrombin, collagen, the endoperoxide analog U-46619 and the calcium ionophore A 23187. Quin2 and fura-2 mediated platelet sensitisation could be due to altered arachidonic acid metabolism since it was inhibited by prior treatment with the cydooxygenase inhibitor acetylsalicylate. In contrast, platelets loaded with higher concentrations of calcium chelators exhibited diminished aggregation responses to all aggregating agents. This latter effect was accompanied by increased fluidity of the platelet plasma membrane bilayer and by the exposure of a new pool of membranes to the outer surface of platelets, as monitored with trimethylammonium- diphenylhexatriene (TMA-DPH) in platelets loaded with the non-fluorescent calcium probe analog MAPT. In contrast, low concentrations of quin2 did not potentiate shape change of platelets activated with ADP. Thus, shape change and aggregation can be influenced separately by intracellular Ca2+ chelators. We conclude that platelet responses are altered by the incorporation of intracellular calcium chelators at concentrations used to monitor intracellular calcium changes.

A mitochondrial uncoupler increases KCa currents but decreases KV currents in pulmonary artery myocytes

1996 ◽  
Vol 270 (1) ◽  
pp. C321-C331 ◽  
Author(s):  
X. J. Yuan ◽  
T. Sugiyama ◽  
W. F. Goldman ◽  
L. J. Rubin ◽  
M. P. Blaustein
Keyword(s):  
Pulmonary Artery ◽  
Fluorescent Imaging ◽  
K Channel ◽  
Metabolic Inhibitor ◽  
Acetoxymethyl Ester ◽  
Atp Production ◽  
Kv Channels ◽  
Kca Channels ◽  
Carbonyl Cyanide ◽  
Microscopy Techniques

Intracellular free Ca2+ concentration ([Ca2+]i) and ATP play important roles in the regulation of K- channels in pulmonary artery (PA) myocytes. Previous studies have demonstrated that hypoxia and the metabolic inhibitor, 2-deoxy-D-glucose, decrease voltage-gated K+ (KV) currents [IK(V)] and thereby depolarize PA myocytes; these effects lead to a rise in [Ca2+]i. Here, we used carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP), a protonophore that uncouples mitochondrial respiration from ATP production, to test whether the inhibition of oxidative phosphorylation affects K+ channel activities in rat PA myocytes. Patch-clamp and fluorescent-imaging microscopy techniques were used to measure K+ currents (IK) and [Ca2+]i, respectively. FCCP (3-5 microM) reversibly raised [Ca2-]i in the presence and absence of external Ca2+. This effect was prevented by pretreating the cells with the membrane-permeable Ca2+ chelator, 1,2-bis(2-amino-phenoxy) ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). This suggests that much of the FCCP-evoked rise in [Ca2-]i was due to Ca2+ release from intracellular stores. Brief exposure to FCCP (approximately 2 min) reversibly enhanced Ik. This augmentation was not influenced by glibenclamide, an ATP-sensitive K channel blocker, but was eliminated by pretreatment with BAPTA-AM. This implies that the FCCP-evoked rise in [Ca2+]i activated Ca(2+)-activated K- (Kca) channels. Furthermore, in BAPTA-treated cells, longer application (> or = 6 min) of FCCP reversibly decreased IK(V) in PA cells bathed in Ca(2+)-free solution. These results demonstrate that FCCP affects KCa and Kv channels by different mechanisms. FCCP increases IK[Ca] by raising [Ca2+]i primarily as a result of Ca2+ release, but decreases IK(V) by a Ca(2+)-independent mechanism, presumably the inhibition of oxidative ATP production.

ST1926, a novel and orally active retinoid-related molecule inducing apoptosis in myeloid leukemia cells: modulation of intracellular calcium homeostasis

Blood ◽  
2004 ◽  
Vol 103 (1) ◽  
pp. 194-207 ◽  
Author(s):  
Enrico Garattini ◽  
Edoardo Parrella ◽  
Luisa Diomede ◽  
Maurizio Gianni' ◽  
Yesim Kalac ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Intracellular Calcium ◽  
Mechanism Of Action ◽  
Severe Combined Immunodeficiency ◽  
Leukemia Cell ◽  
Myelogenous Leukemia ◽  
Acetoxymethyl Ester ◽  
Calcium Blockers ◽  
Orally Active

Abstract Retinoid-related molecules (RRMs) are derivatives of retinoic acid and promising antileukemic agents with a mechanism of action different from that of other common chemotherapeutics. Here, we describe a novel chemical series designed against the RRM prototype, CD437. This includes molecules with apoptotic effects in acute promyelocytic leukemia and other myelogenous leukemia cell lines, as well as ST2065, an RRM with antagonistic properties. The most interesting apoptotic agent is ST1926, a compound more powerful than CD437 in vitro and orally active in vivo on severe combined immunodeficiency (SCID) mice that received transplants of NB4 cells. ST1926 has the same mechanism of action of CD437, as indicated by the ability to trans-activate retinoic acid receptor γ, to induce the phosphorylation of p38 and JNK, and to down-regulate the expression of many genes negatively modulated by CD437. ST1926 causes an immediate increase in the cytosolic levels of calcium that are directly related to the apoptotic potential of the RRMs considered. The intracellular calcium elevation is predominantly the result of an inhibition of the mitochondrial calcium uptake. The phenomenon is blocked by the ST2065 antagonist, the intracellular calcium chelator BAPTA (1,2 bis (2-aminophenoxy) ethane-N, N, N′,N′-tetraacetic acid tetrakis (acetoxymethyl ester), and by high concentrations of calcium blockers of the dihydropyridine type, compounds that suppress ST1926-induced apoptosis.

scholarly journals Poly-arginine-18 (R18) Confers Neuroprotection through Glutamate Receptor Modulation, Intracellular Calcium Reduction, and Preservation of Mitochondrial Function

Molecules ◽  
2020 ◽  
Vol 25 (13) ◽  
pp. 2977
Author(s):  
Gabriella MacDougall ◽  
Ryan S. Anderton ◽  
Amy Trimble ◽  
Frank L. Mastaglia ◽  
Neville W. Knuckey ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Glutamate Receptor ◽  
Cortical Neurons ◽  
Calcium Influx ◽  
Ros Generation ◽  
Neuronal Cultures ◽  
Atp Production ◽  
Endoplasmic Reticulum Calcium ◽  
Receptor Modulation ◽  
Insight Into

Recent studies have highlighted that a novel class of neuroprotective peptide, known as cationic arginine-rich peptides (CARPs), have intrinsic neuroprotective properties and are particularly effective anti-excitotoxic agents. As such, the present study investigated the mechanisms underlying the anti-excitotoxic properties of CARPs, using poly-arginine-18 (R18; 18-mer of arginine) as a representative peptide. Cortical neuronal cultures subjected to glutamic acid excitotoxicity were used to assess the effects of R18 on ionotropic glutamate receptor (iGluR)-mediated intracellular calcium influx, and its ability to reduce neuronal injury from raised intracellular calcium levels after inhibition of endoplasmic reticulum calcium uptake by thapsigargin. The results indicate that R18 significantly reduces calcium influx by suppressing iGluR overactivation, and results in preservation of mitochondrial membrane potential (ΔΨm) and ATP production, and reduced ROS generation. R18 also protected cortical neurons against thapsigargin-induced neurotoxicity, which indicates that the peptide helps maintain neuronal survival when intracellular calcium levels are elevated. Taken together, these findings provide important insight into the mechanisms of action of R18, supporting its potential application as a neuroprotective therapeutic for acute and chronic neurological disorders.

scholarly journals Platelet activating factor raises intracellular calcium ion concentration in macrophages.

1986 ◽  
Vol 103 (2) ◽  
pp. 439-450 ◽  
Author(s):  
G W Conrad ◽  
T J Rink
Keyword(s):  
Heavy Metals ◽  
Intracellular Calcium ◽  
Calcium Ion ◽  
Platelet Activating Factor ◽  
Ion Concentration ◽  
Early Event ◽  
Acetoxymethyl Ester ◽  
Intracellular Calcium Ion ◽  
The Times ◽  
Calcium Ion Concentration

Peritoneal cells from thioglycollate-stimulated mice were allowed to adhere to coverglasses for 2 h to give a dense monolayer of adherent cells greater than 95% of which were macrophages. After incubation with the tetra-acetoxymethyl ester of quin2, coverglasses were rinsed with Ca2+-free saline, oriented at a 45 degree angle in square cuvettes containing a magnetically driven stir bar, and analyzed for changes in quin2 fluorescence in a spectrofluorimeter. Such fluorescence, taken as an indication of intracellular calcium ion concentration ([Ca2+]i), increased as exogenous calcium ion concentration ([Ca2+]o) was raised to 1 mM. At [Ca2+]o approximately equal to 10 microM, [Ca2+]i = 72 +/- 14 nM (n = 26); at [Ca2+]o = 1 mM, [Ca2+]i = 140-220 nM, levels not increased by N, N, N', N'-tetrakis (2-pyridylmethyl) ethylenediamine, a membrane-permeant chelator of heavy metals than can quench quin2. Addition of mouse alpha + beta fibroblast interferon, lipopolysaccharide, thrombin, collagen, vasopressin, ADP, compound 48/80, or U46619 did not change [Ca2+]i. However, addition of platelet activating factor (PAF) (2-20 ng/ml) raised [Ca2+]i by 480 nM within 1 min if [Ca2+]o = 1 mM. In the presence of 5 mM EGTA, PAF raised [Ca2+]i by 25 nM. This suggests that PAF causes influx of exogenous Ca2+, as well as releasing some Ca2+ from intracellular stores. Consistent with these results, when PAF was added to 1 mM Ca2+ in the presence of 100 microM Cd2+ or Mn2+ to block Ca2+ influx, [Ca2+]i increased by only intermediate amounts; at the times of such dampened peak response, [Ca2+]i could be raised within 1 min to normal PAF-stimulated levels by chelation of the exogenous heavy metals with diethylenetriaminepentaacetic acid. Normal PAF responses were observed in the presence of indomethacin. The lowest dose of PAF observed to raise [Ca2+]i was 0.1 ng/ml. Response of [Ca2+]i to 2-20 ng/ml PAF was transient, and second applications had no effect. The PAF response also was seen in cell suspensions. These results suggest that an increase in [Ca2+]i may be an early event in PAF activation of macrophages.

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