Effects of 2,5-di(tert-butyl)-1,4-Hydroquinone, an Endoplasmic Reticulum Ca2+-ATPase Inhibitor, on Agonist-Stimulated Phasic Myometrial Contractions

1995 ◽  
Vol 207 (3) ◽  
pp. 891-896 ◽  
Author(s):  
M. Phillippe ◽  
J. Kim ◽  
M. Freij ◽  
T. Saunders
Keyword(s):  
Endoplasmic Reticulum ◽  
Atpase Inhibitor ◽  
Tert Butyl

Abstract 138: High Salt Intake Augments Excitability of Pre-sympathetic PVN Neurons Through Dysfunction of the Endoplasmic Reticulum Ca2+ ATPase

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Robert A Larson ◽  
Andrew D Chapp ◽  
Michael J Huber ◽  
Zixi Cheng ◽  
Zhiying Shan ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Salt Intake ◽  
Sympathetic Neurons ◽  
High Salt ◽  
Ventrolateral Medulla ◽  
Dependent Manner ◽  
Loss Of Function ◽  
Atpase Inhibitor ◽  
High Salt Intake ◽  
Significant Difference

High salt (HS) intake sensitizes pre-sympathetic neurons in the hypothalamic paraventricular nucleus (PVN) leading to augmented neuronal excitability. Recently, we reported that dysfunction of Ca 2+ dependent K + channels in the PVN contributes to HS intake induced sympathoexcitation. The endoplasmic reticulum (ER) acts as a Ca 2+ store and plays an important role in regulating intracellular Ca 2+ homeostasis. The ER Ca 2+ ATPase is responsible for maintaining the high level of ER Ca 2+ and loss of function would deplete the Ca 2+ store contributing to the reduced activity of Ca 2+ dependent K + channels. We hypothesized that a 2% (NaCl) HS diet for 5 weeks would reduce function of the ER Ca 2+ ATPase and augment excitability of PVN neurons with axon projections to the rostral ventrolateral medulla (PVN-RVLM) identified by retrograde label. In whole cell current-clamp recordings from PVN-RVLM neurons, graded current injections evoked graded increases in spike frequency. Maximum discharge was evoked by +200 pA injections and averaged 22±2 Hz (n=6) in normal salt (NS) control and was significantly augmented (p<0.05) by HS diet 34±5 Hz (n=8). Bath application of thapsigargin (TG) (0.5 μM), the ER Ca 2+ ATPase inhibitor, augmented excitability of PVN-RVLM neurons in NS (32±4 Hz, n=5, p<0.05), yet had no significant effect in HS rats (32±6 Hz, n=6). ER Ca 2+ ATPase function was assessed in whole animal preparations by bilateral PVN microinjection of TG in anesthetized rats. PVN microinjection of TG (0.15, 0.3 0.75 and 1.5 nmol/100nl) increased sympathetic nerve activity (SNA) and mean arterial pressure (MAP) in a dose-dependent manner in NS rats. Maximum increases in splanchnic SNA (SSNA), renal SNA (RSNA) and MAP elicited by PVN TG (0.75 nmol/100nl; n=5) were 93±7%, 75±7%, and 11±2mmHg, respectively. In contrast, sympathoexcitatory responses to PVN TG (0.75 nmol/100nl; n=5) were attenuated in HS treated rats (SSNA 41±8%, RSNA 22±5%, p<0.05 vs. NS) while MAP responses demonstrated no significant difference (+8±2 mmHg, p>0.05 vs NS). Our data indicate that a HS diet reduces ER Ca 2+ ATPase activity and augments excitability of PVN-RVLM neurons in vitro. Altered ER Ca 2+ homeostasis may contribute to sympathoexcitation through loss of Ca 2+ dependent K + channel activity in the PVN.

scholarly journals Acidocalcisomes in Toxoplasma gondii tachyzoites

1996 ◽  
Vol 313 (2) ◽  
pp. 655-659 ◽  
Author(s):  
Silvia N. J. MORENO ◽  
Li ZHONG
Keyword(s):  
Endoplasmic Reticulum ◽  
Toxoplasma Gondii ◽  
Mammalian Cells ◽  
Specific Inhibitor ◽  
Mitochondrial Atpase ◽  
Bafilomycin A1 ◽  
Atpase Inhibitor ◽  
Extracellular Medium ◽  
Acidic Compartment ◽  
Acidic Organelles

Toxoplasma gondii tachyzoites were loaded with the fluorescent indicator fura 2 to investigate the transport mechanisms involved in maintaining their intracellular Ca2+ homoeostasis. The mitochondrial ATPase inhibitor oligomycin and the endoplasmic-reticulum Ca2+-ATPase inhibitor thapsigargin increased the intracellular Ca2+ concentration ([Ca2+]i), thus indicating the requirement for ATP and the involvement of the endoplasmic reticulum in maintaining intracellular Ca2+ homoeostasis. The effect of thapsigargin was more accentuated in the presence of extracellular Ca2+, clearly showing that, as occurs with other eukaryotic cells, depletion of intracellular Ca2+ pools led to an increase in the uptake of Ca2+ from the extracellular medium. In addition to these results, we found evidence that, in contrast with what occurs in mammalian cells, T. gondii tachyzoites possess a significant amount of Ca2+ stored in an acidic compartment, termed the acidocalcisome, as indicated by: (1) the increase in [Ca2+]i induced by bafilomycin A1 (a specific inhibitor of H+-ATPases), nigericin (a K+/H+ exchanger) or the weak base NH4Cl, in the nominal absence of extracellular Ca2+ to preclude Ca2+ entry; and (2) the effect of ionomycin, a Ca2+-releasing ionophore that cannot take Ca2+ out of acidic organelles and that was more effective after alkalinization of these compartments by addition of bafilomycin A1, nigericin or NH4Cl. Considering the relative importance of the ionomycin-releasable and the ionomycin+NH4Cl-releasable Ca2+ pools, it is apparent that T. gondii tachyzoites contain a significant amount of Ca2+ stored in acidocalcisomes.

Sarcoplasmic-endoplasmic reticulum Ca2+-ATPase inhibition prevents endothelin A receptor antagonism in rat aorta

2007 ◽  
Vol 292 (4) ◽  
pp. H1961-H1966 ◽  
Author(s):  
M. Tosun ◽  
Y. Erac ◽  
C. Selli ◽  
N. Karakaya
Keyword(s):  
Endoplasmic Reticulum ◽  
Receptor Antagonist ◽  
Cyclopiazonic Acid ◽  
Rat Aorta ◽  
Endothelin Receptor Antagonist ◽  
Endothelin Receptor ◽  
Atpase Inhibitor ◽  
Endothelin 1 ◽  
Endothelin A Receptor ◽  
Endothelin A

This study tested whether sarcoplasmic-endoplasmic reticulum Ca2+-ATPase regulates the ability of endothelin receptor antagonist to inhibit the endothelin-1 constriction. The endothelin A receptor antagonist BQ-123 (1 μM) completely relaxed constriction to 10 nM endothelin-1 in endothelium-denuded rat aorta. Challenge with cyclopiazonic acid (10 μM), a sarcoplasmic-endoplasmic reticulum Ca2+-ATPase inhibitor, during the plateau of endothelin-1 constriction enhanced the constriction by ∼30%. BQ-123 relaxed the endothelin-1 plus cyclopiazonic acid constriction by only ∼10%. In contrast, prazosin (1 μM), an α-adrenergic receptor antagonist, still completely relaxed the 0.3 μM phenylephrine constriction in the presence of cyclopiazonic acid. Verapamil relaxed the endothelin-1 plus cyclopiazonic acid constriction by ∼30%, whereas Ni2+ and 2-aminoethoxydiphenyl borate, nonselective cation channel and store-operated channel blockers, respectively, completely relaxed the constriction. These results suggest that lowered sarcoplasmic-endoplasmic reticulum Ca2+-ATPase activity selectively decreases the ability of endothelin receptor antagonist to inhibit the endothelin A receptor. The decreased antagonism may be related to the opening of store-operated channels and subsequent greater internalization of endothelin A receptor.

scholarly journals Store-operated influx of Ca2+ in pancreatic β-cells exhibits graded dependence on the filling of the endoplasmic reticulum

2001 ◽  
Vol 114 (11) ◽  
pp. 2179-2186 ◽  
Author(s):  
Oleg Dyachok ◽  
Erik Gylfe
Keyword(s):  
Endoplasmic Reticulum ◽  
Channel Blocker ◽  
Cyclopiazonic Acid ◽  
Atpase Inhibitor ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Rate Of Increase ◽  
Voltage Dependent ◽  
Individual Mouse ◽  
Extracellular Ions

The store-operated pathway for Ca2+ entry was studied in individual mouse pancreatic β-cells by measuring the cytoplasmic concentrations of Ca2+ ([Ca2+]i) and Mn2+ ([Mn2+]i) with the fluorescent indicator fura-2. Influx through the store-operated pathway was initially shut off by pre-exposure to 20 mM glucose, which maximally stimulates intracellular Ca2+ sequestration. To avoid interference with voltage-dependent Ca2+ entry the cells were hyperpolarized with diazoxide and the channel blocker methoxyverapamil was present. Activation of the store-operated pathway in response to Ca2+ depletion of the endoplasmic reticulum was estimated from the sustained elevation of [Ca2+]i or from the rate of increase in [Mn2+]i due to influx of these extracellular ions. Increasing concentrations of the inositol 1,4,5-trisphosphate-generating agonist carbachol or the sarco(endo)plasmatic reticulum Ca2+-ATPase inhibitor cyclopiazonic acid (CPA) cause gradual activation of the store-operated pathway. In addition, the carbachol- and CPA-induced influx of Mn2+ depended on store filling in a graded manner. The store-operated influx of Ca2+/Mn2+ was inhibited by Gd3+ and 2-aminoethoxydiphenyl borate but neither of these agents discriminated between store-operated and voltage-dependent entry. The finely tuned regulation of the store-operated mechanisms in the β-cell has direct implications for the control of membrane potential and insulin secretion.

Evidence for two intracellular calcium pools in Dictyostelium: the cAMP-induced calcium influx is directed into a NBD-Cl- and 2,5-di-(tert-butyl)1,4-hydroquinone-sensitive pool

1993 ◽  
Vol 105 (4) ◽  
pp. 1131-1135 ◽  
Author(s):  
H. Flaadt ◽  
E. Jaworski ◽  
D. Malchow
Keyword(s):  
Calcium Influx ◽  
Fine Tuning ◽  
Cell Surface Receptor ◽  
Bafilomycin A1 ◽  
Atpase Inhibitor ◽  
Tert Butyl ◽  
Cellular Events ◽  
Surface Receptor ◽  
Oriented Movement ◽  
Gamma S

Signal transduction in Dictyostelium for oriented movement and differentiation involves a fine tuning of the cytosolic Ca2+ concentration. We have previously shown that cAMP binding to the cell surface receptor elicits two cellular events: (i) to enhance Ca2+ entry across the plasma membrane; (ii) to increase Ca2+ uptake into Ca(2+)-sequestering organelles. Here we used permeabilised cells to show that cAMP-induced Ca2+ uptake in these cells was sensitive to the Ca2+ transport ATPase blocker 2,5-di-(tert-butyl)-1,4-hydroquinone (BHQ) and the vacuolar H(+)-ATPase inhibitor NBD-Cl. By contrast, bafilomycin A1 and vanadate, inhibitors of Ca2+ uptake into acidosomes in Dictyostelium, did not reduce the cAMP-induced Ca2+ uptake of permeabilised cells. GTP gamma S served as a tool to measure Ins(1,4,5)P3- (InsP3)-sensitive Ca2+ release. Following NBD-Cl or BHQ treatment Ca2+ release was reversibly inhibited. We conclude that the cAMP-controlled Ca2+ influx is directed into a NBD-Cl and BHQ-sensitive compartment, which comprises the InsP3-releasable pool. The acidosomal Ca2+ store seems to provide for additional Ca2+ if required.

scholarly journals Two distinct calcium pools in the endoplasmic reticulum of HEK-293T cells

2011 ◽  
Vol 435 (1) ◽  
pp. 227-235 ◽  
Author(s):  
Francisco J. Aulestia ◽  
Pedro C. Redondo ◽  
Arancha Rodríguez-García ◽  
Juan A. Rosado ◽  
Ginés M. Salido ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Hela Cells ◽  
Simian Virus 40 ◽  
Cyclopiazonic Acid ◽  
Simian Virus ◽  
T Antigen ◽  
Atpase Inhibitor ◽  
Ph Gradients ◽  
293 Cells ◽  
Functional Features

Agonist-sensitive intracellular Ca2+ stores may be heterogeneous and exhibit distinct functional features. We have studied the properties of intracellular Ca2+ stores using targeted aequorins for selective measurements in different subcellular compartments. Both, HEK-293T [HEK (human embryonic kidney)-293 cells expressing the large T-antigen of SV40 (simian virus 40)] and HeLa cells accumulated Ca2+ into the ER (endoplasmic reticulum) to near millimolar concentrations and the IP3-generating agonists, carbachol and ATP, mobilized this Ca2+ pool. We find in HEK-293T, but not in HeLa cells, a distinct agonist-releasable Ca2+ pool insensitive to the SERCA (sarco/endoplasmic reticulum Ca2+ ATPase) inhibitor TBH [2,5-di-(t-butyl)-benzohydroquinone]. TG (thapsigargin) and CPA (cyclopiazonic acid) completely emptied this pool, whereas lysosomal disruption or manoeuvres collapsing endomembrane pH gradients did not. Our results indicate that SERCA3d is important for filling the TBH-resistant store as: (i) SERCA3d is more abundant in HEK-293T than in HeLa cells; (ii) the SERCA 3 ATPase activity of HEK-293T cells is not fully blocked by TBH; and (iii) the expression of SERCA3d in HeLa cells generated a TBH-resistant agonist-mobilizable compartment in the ER. Therefore the distribution of SERCA isoforms may originate the heterogeneity of the ER Ca2+ stores and this may be the basis for store specialization in diverse functions. This adds to recent evidence indicating that SERCA3 isoforms may subserve important physiological and pathophysiological mechanisms.

Sign in / Sign up

Export Citation Format

Share Document