Articoli di riviste: "Sodium/calcium exchanger (NCX)"

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Chovancova, Barbora, Veronika Liskova, Petr Babula e Olga Krizanova. "Role of Sodium/Calcium Exchangers in Tumors". Biomolecules 10, n. 9 (31 agosto 2020): 1257. http://dx.doi.org/10.3390/biom10091257.

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Abstract (sommario):

The sodium/calcium exchanger (NCX) is a unique calcium transport system, generally transporting calcium ions out of the cell in exchange for sodium ions. Nevertheless, under special conditions this transporter can also work in a reverse mode, in which direction of the ion transport is inverted—calcium ions are transported inside the cell and sodium ions are transported out of the cell. To date, three isoforms of the NCX have been identified and characterized in humans. Majority of information about the NCX function comes from isoform 1 (NCX1). Although knowledge about NCX function has evolved rapidly in recent years, little is known about these transport systems in cancer cells. This review aims to summarize current knowledge about NCX functions in individual types of cancer cells.

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Chernysh, Olga, Madalina Condrescu e John P. Reeves. "Sodium-dependent inactivation of sodium/calcium exchange in transfected Chinese hamster ovary cells". American Journal of Physiology-Cell Physiology 295, n. 4 (ottobre 2008): C872—C882. http://dx.doi.org/10.1152/ajpcell.00221.2008.

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High concentrations of cytosolic Na+ ions induce the time-dependent formation of an inactive state of the Na+/Ca2+ exchanger (NCX), a process known as Na+-dependent inactivation. NCX activity was measured as Ca2+ uptake in fura 2-loaded Chinese hamster ovary (CHO) cells expressing the wild-type (WT) NCX or mutants that are hypersensitive (F223E) or resistant (K229Q) to Na+-dependent inactivation. As expected, 1) Na+-dependent inactivation was promoted by high cytosolic Na+ concentration, 2) the F223E mutant was more susceptible than the WT exchanger to inactivation, whereas the K229Q mutant was resistant, and 3) inactivation was enhanced by cytosolic acidification. However, in contrast to expectations from excised patch studies, 1) the WT exchanger was resistant to Na+-dependent inactivation unless cytosolic pH was reduced, 2) reducing cellular phosphatidylinositol-4,5-bisphosphate levels did not induce Na+-dependent inactivation in the WT exchanger, 3) Na+-dependent inactivation did not increase the half-maximal cytosolic Ca2+ concentration for allosteric Ca2+ activation, 4) Na+-dependent inactivation was not reversed by high cytosolic Ca2+ concentrations, and 5) Na+-dependent inactivation was partially, but transiently, reversed by an increase in extracellular Ca2+ concentration. Thus Na+-dependent inactivation of NCX expressed in CHO cells differs in several respects from the inactivation process measured in excised patches. The refractoriness of the WT exchanger to Na+-dependent inactivation suggests that this type of inactivation is unlikely to be a strong regulator of exchange activity under physiological conditions but would probably act to inhibit NCX-mediated Ca2+ influx during ischemia.

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Roome, Chris J., Emmet M. Power e Ruth M. Empson. "Transient reversal of the sodium/calcium exchanger boosts presynaptic calcium and synaptic transmission at a cerebellar synapse". Journal of Neurophysiology 109, n. 6 (15 marzo 2013): 1669–80. http://dx.doi.org/10.1152/jn.00854.2012.

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Abstract (sommario):

The sodium/calcium exchanger (NCX) is a widespread transporter that exchanges sodium and calcium ions across excitable membranes. Normally, NCX mainly operates in its “forward” mode, harnessing the electrochemical gradient of sodium ions to expel calcium. During membrane depolarization or elevated internal sodium levels, NCX can instead switch the direction of net flux to expel sodium and allow calcium entry. Such “reverse”-mode NCX operation is frequently implicated during pathological or artificially extended periods of depolarization, not during normal activity. We have used fast calcium imaging, mathematical simulation, and whole cell electrophysiology to study the role of NCX at the parallel fiber-to-Purkinje neuron synapse in the mouse cerebellum. We show that nontraditional, reverse-mode NCX activity boosts the amplitude and duration of parallel fiber calcium transients during short bursts of high-frequency action potentials typical of their behavior in vivo. Simulations, supported by experimental manipulations, showed that accumulation of intracellular sodium drove NCX into reverse mode. This mechanism fueled additional calcium influx into the parallel fibers that promoted synaptic transmission to Purkinje neurons for up to 400 ms after the burst. Thus we provide the first functional demonstration of transient and fast NCX-mediated calcium entry at a major central synapse. This unexpected contribution from reverse-mode NCX appears critical for shaping presynaptic calcium dynamics and transiently boosting synaptic transmission, and is likely to optimize the accuracy of cerebellar information transfer.

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Smith, L., e J. B. Smith. "Activation of adenylyl cyclase downregulates sodium/calcium exchanger of arterial myocytes". American Journal of Physiology-Cell Physiology 269, n. 6 (1 dicembre 1995): C1379—C1384. http://dx.doi.org/10.1152/ajpcell.1995.269.6.c1379.

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Chronic elevation of adenosine 3',5'-cyclic monophosphate (cAMP) is known to inhibit the proliferation of cultured vascular smooth muscle cells. The present findings show that the activation of adenylyl cyclase with forskolin decreased Na+/Ca2+ exchanger (NCX) mRNA and activity. Fetal bovine serum restored NCX transcript and activity. The changes in NCX transcript preceded the changes in NCX activity. Incubation of low-passage immortalized myocytes with forskolin plus 3-isobutyl-1-methylxanthine (IBMX), which inhibits cAMP phosphodiesterase, decreased NCX mRNA by 60% in 6 h and 80% in 24 h. After a 6-h lag, forskolin plus IBMX decreased NCX activity almost linearly to 20% of control at 40 h. 1,9-Dideoxyforskolin, which does not activate adenylyl cyclase, had no effect on NCX mRNA or activity. Forskolin plus IBMX decreased the c-Myc transcript, an immediate-early gene whose expression correlates with cell proliferation, but had no effect on plasma membrane Ca(2+)-ATPase transcripts. Removal of forskolin plus IBMX and addition of fetal bovine serum increased NCX and c-Myc transcripts seven- to eightfold in 6 h and restored NCX activity in 24 h. Inhibition of protein or RNA synthesis by cycloheximide or actinomycin D, respectively, prevented the increase in NCX mRNA. In contrast to blocking NCX induction, cycloheximide potentiated c-Myc induction by serum. Transcription factors that regulate myocyte growth may mediate the opposing influences of serum and forskolin on NCX mRNA and activity.

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Münch, Götz, Kai Rosport, Christine Baumgartner, Zhongmin Li, Silvia Wagner, Andreas Bültmann e Martin Ungerer. "Functional alterations after cardiac sodium-calcium exchanger overexpression in heart failure". American Journal of Physiology-Heart and Circulatory Physiology 291, n. 2 (agosto 2006): H488—H495. http://dx.doi.org/10.1152/ajpheart.01324.2005.

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The sodium-calcium exchanger (NCX) is discussed as one of the key proteins involved in heart failure. However, the causal role and the extent to which NCX contributes to contractile dysfunction during heart failure are poorly understood. NCX overexpression was induced by infection with an adenovirus coding for NCX, which coexpressed green fluorescence protein (GFP) (AdNCX) by ex vivo gene transfer to nonfailing and failing rabbit cardiomyocytes. Myocardial gene transfer in rabbits in vivo was achieved by adenoviral delivery via aortic cross-clamping. Peak cell shortening of cardiomyocytes was determined photo-optically. Hemodynamic parameters in vivo were determined by echocardiography (fractional shortening) and tip catheter [maximal first derivative of left ventricular (LV) pressure (dP/d tmax); maximal negative derivative of LV pressure (−dP/d tmax)]. Peak cell shortening was depressed after NCX gene delivery in isolated nonfailing and in failing cardiomyocytes. In nonfailing rabbits in vivo, basal systolic contractility (fractional shortening and dP/d tmax) and maximum rate of LV relaxation (−dP/d tmax) in vivo were largely unaffected after NCX overexpression. However, during heart failure, long-term NCX overexpression over 2 wk significantly improved fractional shortening and dP/d tmax compared with AdGFP-infected rabbits, both without inotropic stimulation and after β-adrenergic stimulation with isoproterenol. −dP/d tmax was also improved after NCX overexpression in the failing rabbits group. These results indicate that short-term effects of NCX overexpression impair contractility of isolated failing and nonfailing rabbit cardiomyocytes. NCX overexpression over 2 wk in vivo does not seem to affect myocardial contractility in nonfailing rabbits. Interestingly, in vivo overexpression of NCX decreased the progression of systolic and diastolic contractile dysfunction and improved β-adrenoceptor-mediated contractile reserve in heart failure in rabbits in vivo.

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Torrente, Angelo G., Rui Zhang, Audrey Zaini, Jorge F. Giani, Jeanney Kang, Scott T. Lamp, Kenneth D. Philipson e Joshua I. Goldhaber. "Burst pacemaker activity of the sinoatrial node in sodium–calcium exchanger knockout mice". Proceedings of the National Academy of Sciences 112, n. 31 (20 luglio 2015): 9769–74. http://dx.doi.org/10.1073/pnas.1505670112.

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In sinoatrial node (SAN) cells, electrogenic sodium–calcium exchange (NCX) is the dominant calcium (Ca) efflux mechanism. However, the role of NCX in the generation of SAN automaticity is controversial. To investigate the contribution of NCX to pacemaking in the SAN, we performed optical voltage mapping and high-speed 2D laser scanning confocal microscopy (LSCM) of Ca dynamics in an ex vivo intact SAN/atrial tissue preparation from atrial-specific NCX knockout (KO) mice. These mice lack P waves on electrocardiograms, and isolated NCX KO SAN cells are quiescent. Voltage mapping revealed disorganized and arrhythmic depolarizations within the NCX KO SAN that failed to propagate into the atria. LSCM revealed intermittent bursts of Ca transients. Bursts were accompanied by rising diastolic Ca, culminating in long pauses dominated by Ca waves. The L-type Ca channel agonist BayK8644 reduced the rate of Ca transients and inhibited burst generation in the NCX KO SAN whereas the Ca buffer 1,2-Bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (acetoxymethyl ester) (BAPTA AM) did the opposite. These results suggest that cellular Ca accumulation hinders spontaneous depolarization in the NCX KO SAN, possibly by inhibiting L-type Ca currents. The funny current (If) blocker ivabradine also suppressed NCX KO SAN automaticity. We conclude that pacemaker activity is present in the NCX KO SAN, generated by a mechanism that depends upon If. However, the absence of NCX-mediated depolarization in combination with impaired Ca efflux results in intermittent bursts of pacemaker activity, reminiscent of human sinus node dysfunction and “tachy-brady” syndrome.

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Haug-Collet, K., B. Pearson, R. Webel, R. T. Szerencsei, R. J. Winkfein, P. P. M. Schnetkamp e N. J. Colley. "Cloning and Characterization of a Potassium-Dependent Sodium/Calcium Exchanger in Drosophila". Journal of Cell Biology 147, n. 3 (1 novembre 1999): 659–70. http://dx.doi.org/10.1083/jcb.147.3.659.

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Sodium/calcium(-potassium) exchangers (NCX and NCKX) are critical for the rapid extrusion of calcium, which follows the stimulation of a variety of excitable cells. To further understand the mechanisms of calcium regulation in signaling, we have cloned a Drosophila sodium/calcium-potassium exchanger, Nckx30C. The overall deduced protein topology for NCKX30C is similar to that of mammalian NCKX, having five membrane-spanning domains in the NH2 terminus separated from six at the COOH-terminal end by a large intracellular loop. We show that NCKX30C functions as a potassium-dependent sodium/calcium exchanger, and is not only expressed in adult neurons as was expected, but is also expressed during ventral nerve cord development in the embryo and in larval imaginal discs. Nckx30C is expressed in a dorsal–ventral pattern in the eye-antennal disc in a pattern that is similar to, but broader than that of wingless, suggesting that large fluxes of calcium may be occurring during imaginal disc development. Nckx30C may not only function in the removal of calcium and maintenance of calcium homeostasis during signaling in the adult, but may also play a critical role in signaling during development.

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de Ruijter, Wouter, Ger J. M. Stienen, Jan van Klarenbosch e Jacob J. de Lange. "Negative and Positive Inotropic Effects of Propofol via L-type Calcium Channels and the Sodium-Calcium Exchanger in Rat Cardiac Trabeculae". Anesthesiology 97, n. 5 (1 novembre 2002): 1146–55. http://dx.doi.org/10.1097/00000542-200211000-00019.

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Background Conflicting opinions are present in the literature regarding the origin of the negative inotropic effect of propofol on the myocardium. This study aims to resolve these discrepancies by investigating the inotropic effects of propofol the L-type calcium channels and the sodium-calcium exchanger (NCX). Methods The effect of 20 microg/ml propofol on force development was determined in rat cardiac trabeculae at different pacing frequencies and different extracellular calcium concentrations. Postrest potentiation, sodium withdrawal during quiescence, and the NCX inhibitor KB-R7943 were used to study changes in the activity of the reverse mode of the NCX by propofol. Results The effect of propofol on steady state peak force depended on pacing frequency and calcium concentration. A negative inotropic effect was observed at pacing frequencies greater than 0.5 Hz, but a positive inotropic effect was observed at 0.1 Hz and low calcium, which cannot be explained by an effect on the L-type calcium channel. Propofol enhanced postrest potentiation in a calcium-dependent manner. Sodium withdrawal during quiescence and the use of the specific NCX inhibitor KB-R7943 provided evidence for an enhancement of calcium influx by propofol the reverse mode of the NCX. Conclusions The effects of propofol on the myocardium depend on pacing frequency and calcium concentration. The positive inotropic effect of propofol is associated with increased calcium influx the reverse mode of the NCX. The authors conclude that the net inotropic effect of propofol is the result of its counteracting influence on the functioning of the L-type calcium channel and the NCX.

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Padín, Juan-Fernando, José-Carlos Fernández-Morales, Román Olivares, Stefan Vestring, Juan-Alberto Arranz-Tagarro, Enrique Calvo-Gallardo, Ricardo de Pascual, Luís Gandía e Antonio G. García. "Plasmalemmal sodium-calcium exchanger shapes the calcium and exocytotic signals of chromaffin cells at physiological temperature". American Journal of Physiology-Cell Physiology 305, n. 2 (15 luglio 2013): C160—C172. http://dx.doi.org/10.1152/ajpcell.00016.2013.

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The activity of the plasmalemmal Na+/Ca2+ exchanger (NCX) is highly sensitive to temperature. We took advantage of this fact to explore here the effects of the NCX blocker KB-R7943 (KBR) at 22 and 37°C on the kinetics of Ca2+ currents ( ICa), cytosolic Ca2+ ([Ca2+]c) transients, and catecholamine release from bovine chromaffin cells (BCCs) stimulated with high K+, caffeine, or histamine. At 22°C, the effects of KBR on those parameters were meager or nil. However, at 37°C whereby the NCX is moving Ca2+ at a rate fivefold higher than at 22°C, various of the effects of KBR were pronounced, namely: 1) no effects on ICa; 2) reduction of the [Ca2+]c transient amplitude and slowing down of its rate of clearance; 3) blockade of the K+-elicited quantal release of catecholamine; 4) blockade of burst catecholamine release elicited by K+; 5) no effect on catecholamine release elicited by short K+ pulses (1–2 s) and blockade of the responses produced by longer K+ pulses (3–5 s); and 6) potentiation of secretion elicited by histamine or caffeine. Furthermore, the more selective NCX blocker SEA0400 also potentiated the secretory responses to caffeine. The results suggest that at physiological temperature the NCX substantially contributes to shaping the kinetics of [Ca2+]c transients and the exocytotic responses elicited by Ca2+ entry through Ca2+ channels as well as by Ca2+ release from the endoplasmic reticulum.

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Loffing, Johannes, Dominique Loffing-Cueni, Victor Valderrabano, Lea Kläusli, Steven C. Hebert, Bernard C. Rossier, Joost G. J. Hoenderop, René J. M. Bindels e Brigitte Kaissling. "Distribution of transcellular calcium and sodium transport pathways along mouse distal nephron". American Journal of Physiology-Renal Physiology 281, n. 6 (1 dicembre 2001): F1021—F1027. http://dx.doi.org/10.1152/ajprenal.0085.2001.

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First published August 15, 2001; 10.1152/ajprenal. 00085.2001.—The organization of Na+ and Ca2+ transport pathways along the mouse distal nephron is incompletely known. We revealed by immunohistochemistry a set of Ca2+ and Na+transport proteins along the mouse distal convolution. The thiazide-sensitive Na+-Cl− cotransporter (NCC) characterized the distal convoluted tubule (DCT). The amiloride-sensitive epithelial Na+ channel (ENaC) colocalized with NCC in late DCT (DCT2) and extended to the downstream connecting tubule (CNT) and collecting duct (CD). In early DCT (DCT1), the basolateral Ca2+-extruding proteins [Na+/Ca2+ exchanger (NCX), plasma membrane Ca2+-ATPase (PCMA)] and the cytoplasmic Ca2+-binding protein calbindin D28K (CB) were found at very low levels, whereas the cytoplasmic Ca2+/Mg2+-binding protein parvalbumin was highly abundant. NCX, PMCA, and CB prevailed in DCT2 and CNT, where we located the apical epithelial Ca2+ channel (ECaC1). Its subcellular localization changed from apical in DCT2 to exclusively cytoplasmic at the end of CNT. NCX and PMCA decreased in parallel with the fading of ECaC1 in the apical membrane. All three of them were undetectable in CD. These findings disclose DCT2 and CNT as major sites for transcellular Ca2+ transport in the mouse distal nephron. Cellular colocalization of Ca2+ and Na+ transport pathways suggests their mutual interactions in transport regulation.

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Linask, Kersti K., Ming-Da Han, Michael Artman e Cheryl A. Ludwig. "Sodium-calcium exchanger (NCX-1) and calcium modulation: NCX protein expression patterns and regulation of early heart development". Developmental Dynamics 221, n. 3 (2001): 249–64. http://dx.doi.org/10.1002/dvdy.1131.

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Jha, Brajesh Kumar, e Amrita Jha. "Two dimensional finite element estimation of calcium ions in presence fo NCX and Buffers in Astrocytes". Boletim da Sociedade Paranaense de Matemática 36, n. 1 (1 gennaio 2018): 151. http://dx.doi.org/10.5269/bspm.v36i1.29137.

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Sodium calcium exchanger (NCX) plays effective role in signal transduction in most of the nerve cells like neuron, astrocytes. Sodium ion affects the cytosolic calcium concentration label in Astrocytes via various channels. This affects the movement of the nerve impulse from one cell to other cell. In this paper two dimensional model is developedin the form of diffusion equation to study the effect of NCX in presence and negligence of buffer in Astrocytes. Finite element method is employed to solve the problem and simulated in Matlab to estimate the affect of various parameter like flux, diffusion coefficient, buffer concentration, etc.

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Li, Sen, Anant Chopra, Wendy Keung, Camie W. Y. Chan, Kevin D. Costa, Chi-Wing Kong, Roger J. Hajjar, Christopher S. Chen e Ronald A. Li. "Sarco/endoplasmic reticulum Ca2+-ATPase is a more effective calcium remover than sodium-calcium exchanger in human embryonic stem cell-derived cardiomyocytes". American Journal of Physiology-Heart and Circulatory Physiology 317, n. 5 (1 novembre 2019): H1105—H1115. http://dx.doi.org/10.1152/ajpheart.00540.2018.

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Human pluripotent stem cell (hPSCs)-derived ventricular (V) cardiomyocytes (CMs) display immature Ca2+–handing properties with smaller transient amplitudes and slower kinetics due to such differences in crucial Ca2+-handling proteins as the poor sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump but robust Na+-Ca2+ exchanger (NCX) activities in human embryonic stem cell (ESC)-derived VCMs compared with adult. Despite their fundamental importance in excitation-contraction coupling, the relative contribution of SERCA and NCX to Ca2+-handling of hPSC-VCMs remains unexplored. We systematically altered the activities of SERCA and NCX in human embryonic stem cell-derived ventricular cardiomyocytes (hESC-VCMs) and their engineered microtissues, followed by examining the resultant phenotypic consequences. SERCA overexpression in hESC-VCMs shortened the decay of Ca2+ transient at low frequencies (0.5 Hz) without affecting the amplitude, SR Ca2+ content and Ca2+ baseline. Interestingly, short hairpin RNA-based NCX suppression did not prolong the transient decay, indicating a compensatory response for Ca2+ removal. Although hESC-VCMs and their derived microtissues exhibited negative frequency-transient/force responses, SERCA overexpression rendered them less negative at high frequencies (>2 Hz) by accelerating Ca2+ sequestration. We conclude that for hESC-VCMs and their microtissues, SERCA, rather than NCX, is the main Ca2+ remover during diastole; poor SERCA expression is the leading cause for immature negative-frequency/force responses, which can be partially reverted by forced expression. Combinatorial approach to mature calcium handling in hESC-VCMs may help shed further mechanistic insights. NEW & NOTEWORTHY In this study of human pluripotent stem cell-derived cardiomyocytes, we studied the role of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and Na+-Ca2+ exchanger (NCX) in Ca2+ handling. Our data support the notion that SERCA is more effective in cytosolic calcium removal than the NCX.

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Kang, Beom Seok, Bo Young Choi, A. Ra Kho, Song Hee Lee, Dae Ki Hong, Jeong Hyun Jeong, Dong Hyeon Kang, Min Kyu Park e Sang Won Suh. "An Inhibitor of the Sodium–Hydrogen Exchanger-1 (NHE-1), Amiloride, Reduced Zinc Accumulation and Hippocampal Neuronal Death after Ischemia". International Journal of Molecular Sciences 21, n. 12 (14 giugno 2020): 4232. http://dx.doi.org/10.3390/ijms21124232.

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Acidosis in the brain plays an important role in neuronal injury and is a common feature of several neurological diseases. It has been reported that the sodium–hydrogen exchanger-1 (NHE-1) is a key mediator of acidosis-induced neuronal injury. It modulates the concentration of intra- and extra-cellular sodium and hydrogen ions. During the ischemic state, excessive sodium ions enter neurons and inappropriately activate the sodium–calcium exchanger (NCX). Zinc can also enter neurons through voltage-gated calcium channels and NCX. Here, we tested the hypothesis that zinc enters the intracellular space through NCX and the subsequent zinc accumulation induces neuronal cell death after global cerebral ischemia (GCI). Thus, we conducted the present study to confirm whether inhibition of NHE-1 by amiloride attenuates zinc accumulation and subsequent hippocampus neuronal death following GCI. Mice were subjected to GCI by bilateral common carotid artery (BCCA) occlusion for 30 min, followed by restoration of blood flow and resuscitation. Amiloride (10 mg/kg, intraperitoneally (i.p.)) was immediately injected, which reduced zinc accumulation and neuronal death after GCI. Therefore, the present study demonstrates that amiloride attenuates GCI-induced neuronal injury, likely via the prevention of intracellular zinc accumulation. Consequently, we suggest that amiloride may have a high therapeutic potential for the prevention of GCI-induced neuronal death.

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Giladi, Moshe, Reut Shor, Michal Lisnyansky e Daniel Khananshvili. "Structure-Functional Basis of Ion Transport in Sodium–Calcium Exchanger (NCX) Proteins". International Journal of Molecular Sciences 17, n. 11 (22 novembre 2016): 1949. http://dx.doi.org/10.3390/ijms17111949.

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Giladi, Moshe, Reuben Hiller, Joel A. Hirsch e Daniel Khananshvili. "Population Shift Underlies Ca2+-induced Regulatory Transitions in the Sodium-Calcium Exchanger (NCX)". Journal of Biological Chemistry 288, n. 32 (24 giugno 2013): 23141–49. http://dx.doi.org/10.1074/jbc.m113.471698.

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Polo-Parada, Luis, e Amol A. Modgi. "Differences in Expression and Function in the Atrium versus Ventricle of the Sodium-Calcium Exchanger in the Embryonic Chicken Heart". ISRN Physiology 2013 (1 settembre 2013): 1–12. http://dx.doi.org/10.1155/2013/921527.

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Abstract (sommario):

Heart function is well known to be dependent on intrinsic electrical activity. This electrical activity is primarily mediated by a combination of interactions among various ionic channels and transporters. In this study, we demonstrate that the Na+-Ca2+ exchanger (NCX) is equally present in both atrial and ventricular cells at early stages of development (st. 13). However, ventricular cells exhibit an increase in NCX messenger ribonucleic acid (mRNA) levels during later stages of development, while levels in atrial cells remain constant. We demonstrate that the current density of the NCX increases with development in the ventricle but remains constant in the atrial cells. Furthermore we demonstrate that the NCX has a major role in shaping the cardiac action potential at early stages mainly in ventricular cells (st. 14) than later mainly in the atrial cells (st. 30).

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Boscia, Francesca, Rosaria Gala, Giuseppe Pignataro, Andrea de Bartolomeis, Maria Cicale, Alberto Ambesi-Impiombato, Gianfranco Di Renzo e Lucio Annunziato. "Permanent Focal Brain Ischemia Induces Isoform-Dependent Changes in the Pattern of Na+/Ca2+ Exchanger Gene Expression in the Ischemic Core, Periinfarct Area, and Intact Brain Regions". Journal of Cerebral Blood Flow & Metabolism 26, n. 4 (17 agosto 2005): 502–17. http://dx.doi.org/10.1038/sj.jcbfm.9600207.

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Dysregulation of sodium [Na+]i and calcium [Ca2+]i homeostasis plays a pivotal role in the pathophysiology of cerebral ischemia. Three gene products of the sodium–calcium exchanger family NCX1, NCX2, and NCX3 couple, in a bidirectional way, the movement of these ions across the cell membrane during cerebral ischemia. Each isoform displays a selective distribution in the rat brain. To determine whether NCX gene expression can be regulated after cerebral ischemia, we used NCX isoform-specific antisense radiolabeled probes to analyze, by radioactive in situ hybridization histochemistry, the pattern of NCX1, NCX2, and NCX3 transcripts in the ischemic core, periinfarct area, as well as in nonischemic brain regions, after 6 and 24 h of permanent middle cerebral artery occlusion (pMCAO) in rats. We found that in the focal region, comprising divisions of the prefrontal, somatosensory, and insular cortices, all three NCX transcripts were downregulated. In the periinfarct area, comprising part of the motor cortex and the lateral compartments of the caudate-putamen, NCX2 messenger ribonucleic acid (mRNA) was downregulated, whereas NCX3 mRNA was significantly upregulated. In remote nonischemic brain regions such as the prelimbic and infralimbic cortices, and tenia tecta, both NCX1 and NCX3 transcripts were upregulated, whereas in the medial caudate-putamen only NCX3 transcripts increased. In all these intact regions, NCX2 signal strongly decreased. These results indicate that NCX gene expression is regulated after pMCAO in a differential manner, depending on the exchanger isoform and region involved in the insult. These data may provide a better understanding of each NCX subtype's pathophysiologic role and may allow researchers to design appropriate pharmacological strategies to treat brain ischemia.

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Boyman, Liron, George S. B. Williams, Daniel Khananshvili, Israel Sekler e W. J. Lederer. "NCLX: The mitochondrial sodium calcium exchanger". Journal of Molecular and Cellular Cardiology 59 (giugno 2013): 205–13. http://dx.doi.org/10.1016/j.yjmcc.2013.03.012.

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Geramipour, Amir, Zsófia Kohajda, Claudia Corici, János Prorok, Zsolt Szakonyi, Kinga Oravecz, Zoltán Márton et al. "The investigation of the cellular electrophysiological and antiarrhythmic effects of a novel selective sodium–calcium exchanger inhibitor, GYKB-6635, in canine and guinea-pig hearts". Canadian Journal of Physiology and Pharmacology 94, n. 10 (ottobre 2016): 1090–101. http://dx.doi.org/10.1139/cjpp-2015-0566.

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Abstract (sommario):

The sodium–calcium exchanger (NCX) is considered as the major transmembrane transport mechanism that controls Ca2+ homeostasis. Its contribution to the cardiac repolarization has not yet been directly studied due to lack of specific inhibitors, so that an urgent need for more selective compounds. In this study, the electrophysiological effects of GYKB-6635, a novel NCX inhibitor, on the NCX, L-type calcium, and main repolarizing potassium currents as well as action potential (AP) parameters were investigated. Ion currents and AP recordings were investigated by applying the whole-cell patch clamp and standard microelectrode techniques in canine heart at 37 °C. Effects of GYKB-6635 were studied in ouabain-induced arrhythmias in isolated guinea-pig hearts. At a concentration of 1 μmol/L, GYKB significantly reduced both the inward and outward NCX currents (57% and 58%, respectively). Even at a high concentration (10 μmol/L), GYKB-6635 did not change the ICaL, the maximum rate of depolarization (dV/dtmax), the main repolarizing K+ currents, and the main AP parameters. GYKB-6635 pre-treatment significantly delayed the time to the development of ventricular fibrillation (by about 18%). It is concluded that GYKB-6635 is a potent and highly selective inhibitor of the cardiac NCX and, in addition, it is suggested to also contribute to the prevention of DAD-based arrhythmias.

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Roberts, Diane E., Archibald McNicol e Ratna Bose. "Mechanism of Collagen Activation in Human Platelets". Journal of Biological Chemistry 279, n. 19 (23 febbraio 2004): 19421–30. http://dx.doi.org/10.1074/jbc.m308864200.

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The mechanism of collagen-induced human platelet activation was examined using Ca2+, Na+, and the pH-sensitive fluorescent dyes calcium green/fura red, sodium-binding benzofuran isophthalate, and 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Administration of a moderate dose of collagen (10 μg/ml) to human platelets resulted in an increase in [Ca2+]iand platelet aggregation. The majority of this increase in [Ca2+]iresulted from the influx of calcium from the extracellular milieu via the Na+/Ca2+exchanger (NCX) functioning in the reverse mode and was reduced in a dose-dependent manner by the NCX inhibitors 5-(4-chlorobenzyl)-2′,4′-dimethylbenzamil (KD50= 4.7 ± 1.1 μm) and KB-R7943 (KD50= 35.1 ± 4.8 μm). Collagen-induced platelet aggregation was dependent on an increase in [Ca2+]iand could be inhibited by chelation of intra- and extracellular calcium through the administration of 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetrakis(acetoxymethyl ester) (BAPTA-AM) and EGTA, respectively, or via the administration of BAPTA-AM to platelets suspended in no-Na+/HEPES buffer. Collagen induced an increase in [Na+]i(23.2 ± 7.6 mm) via the actions of thromboxane A2and, to a lesser extent, of the Na+/H+exchanger. This study demonstrates that the collagen-induced increase in [Ca2+]iis dependent on the concentration of Na+in the extracellular milieu, indicating that the collagen-induced increase in [Na+]icauses the reversal of the NCX, ultimately resulting in an increase in [Ca2+]iand platelet aggregation.

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22

Shlosman, Irina, Fabrizio Marinelli, José D. Faraldo-Gómez e Joseph A. Mindell. "The prokaryotic Na+/Ca2+ exchanger NCX_Mj transports Na+ and Ca2+ in a 3:1 stoichiometry". Journal of General Physiology 150, n. 1 (13 dicembre 2017): 51–65. http://dx.doi.org/10.1085/jgp.201711897.

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Abstract (sommario):

Intracellular Ca2+ signals control a wide array of cellular processes. These signals require spatial and temporal regulation of the intracellular Ca2+ concentration, which is achieved in part by a class of ubiquitous membrane proteins known as sodium–calcium exchangers (NCXs). NCXs are secondary-active antiporters that power the translocation of Ca2+ across the cell membrane by coupling it to the flux of Na+ in the opposite direction, down an electrochemical gradient. Na+ and Ca2+ are translocated in separate steps of the antiport cycle, each of which is thought to entail a mechanism whereby ion-binding sites within the protein become alternately exposed to either side of the membrane. The prokaryotic exchanger NCX_Mj, the only member of this family with known structure, has been proposed to be a good functional and structural model of mammalian NCXs; yet our understanding of the functional properties of this protein remains incomplete. Here, we study purified NCX_Mj reconstituted into liposomes under well-controlled experimental conditions and demonstrate that this homologue indeed shares key functional features of the NCX family. Transport assays and reversal-potential measurements enable us to delineate the essential characteristics of this antiporter and establish that its ion-exchange stoichiometry is 3Na+:1Ca2+. Together with previous studies, this work confirms that NCX_Mj is a valid model system to investigate the mechanism of ion recognition and membrane transport in sodium–calcium exchangers.

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23

Newton, Jamila, Luli Rebecca Akinfiresoye e Prosper N’Gouemo. "Inhibition of the Sodium Calcium Exchanger Suppresses Alcohol Withdrawal-Induced Seizure Susceptibility". Brain Sciences 11, n. 2 (23 febbraio 2021): 279. http://dx.doi.org/10.3390/brainsci11020279.

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Abstract (sommario):

Calcium influx plays important roles in the pathophysiology of seizures, including acoustically evoked alcohol withdrawal-induced seizures (AWSs). One Ca2+ influx route of interest is the Na+/Ca2+ exchanger (NCX) that, when operating in its reverse mode (NCXrev) activity, can facilitate Ca2+ entry into neurons, possibly increasing neuronal excitability that leads to enhanced seizure susceptibility. Here, we probed the involvement of NCXrev activity on AWS susceptibility by quantifying the effects of SN-6 and KB-R7943, potent blockers of isoform type 1 (NCX1rev) and 3 (NCX3rev), respectively. Male, adult Sprague–Dawley rats were used. Acoustically evoked AWSs consisted of wild running seizures (WRSs) that evolved into generalized tonic–clonic seizures (GTCSs). Quantification shows that acute SN-6 treatment at a relatively low dose suppressed the occurrence of the GTCSs (but not WRSs) component of AWSs and markedly reduced the seizure severity. However, administration of KB-R7943 at a relatively high dose only reduced the incidence of GTCSs. These findings demonstrate that inhibition of NCX1rev activity is a putative mechanism for the suppression of alcohol withdrawal-induced GTCSs.

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24

Ibáñez, Ignacio, David Bartolomé-Martín, Dolores Piniella, Cecilio Giménez e Francisco Zafra. "Activity dependent internalization of the glutamate transporter GLT-1 requires calcium entry through the NCX sodium/calcium exchanger". Neurochemistry International 123 (febbraio 2019): 125–32. http://dx.doi.org/10.1016/j.neuint.2018.03.012.

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25

Limbu, Bijay, Kushal Shah, Seth H. Weinberg e Makarand Deo. "Role of Cytosolic Calcium Diffusion in Murine Cardiac Purkinje Cells". Clinical Medicine Insights: Cardiology 10s1 (gennaio 2016): CMC.S39705. http://dx.doi.org/10.4137/cmc.s39705.

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Abstract (sommario):

Cardiac Purkinje cells (PCs) are morphologically and electrophysiologically different from ventricular myocytes and, importantly, exhibit distinct calcium (Ca2+) homeostasis. Recent studies suggest that PCs are more susceptible to action potential (AP) abnormalities than ventricular myocytes; however, the exact mechanisms are poorly understood. In this study, we utilized a detailed biophysical mathematical model of a murine PC to systematically examine the role of cytosolic Ca2+ diffusion in shaping the AP in PCs. A biphasic spatiotemporal Ca2+ diffusion process, as recorded experimentally, was implemented in the model. In this study, we investigated the role of cytosolic Ca2+ dynamics on AP and ionic current properties by varying the effective Ca2+ diffusion rate. It was observed that AP morphology, specifically the plateau, was affected due to changes in the intracellular Ca2+ dynamics. Elevated Ca2+ concentration in the sarcolemmal region activated inward sodium-Ca2+ exchanger (NCX) current, resulting in a prolongation of the AP plateau at faster diffusion rates. Artificially clamping the NCX current to control values completely reversed the alterations in the AP plateau, thus confirming the role of NCX in modifying the AP morphology. Our results demonstrate that cytosolic Ca2+ diffusion waves play a significant role in shaping APs of PCs and could provide mechanistic insights in the increased arrhythmogeneity of PCs.

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26

Oceandy, D., P. J. Stanley, E. J. Cartwright e L. Neyses. "The regulatory function of plasma-membrane Ca2+-ATPase (PMCA) in the heart". Biochemical Society Transactions 35, n. 5 (25 ottobre 2007): 927–30. http://dx.doi.org/10.1042/bst0350927.

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Abstract (sommario):

The PMCA (plasma-membrane Ca2+-ATPase) is a ubiquitously expressed calcium-extruding enzymatic pump important in the control of intracellular calcium concentration. Unlike in non-excitable cells, where PMCA is the only system for calcium extrusion, in excitable cells, such as cardiomyocytes, PMCA has been shown to play only a minor role in calcium homoeostasis compared with the NCX (sodium/calcium exchanger), another system of calcium extrusion. However, increasing evidence points to an important role for PMCA in signal transduction; of particular interest in cardiac physiology is the modulation of nNOS (neuronal nitric oxide synthase) by isoform 4b of PMCA. In the present paper, we will discuss recent advances that support a key role for PMCA4 in modulating the nitric oxide signalling pathway in the heart.

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27

TEWARI, SHIVENDRA G., e K. R. PARDASANI. "MODELING EFFECT OF SODIUM PUMP ON CALCIUM OSCILLATIONS IN NEURON CELLS". Journal of Multiscale Modelling 04, n. 03 (settembre 2012): 1250010. http://dx.doi.org/10.1142/s1756973712500102.

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Abstract (sommario):

Calcium plays a significant role in a number of processes like muscle contraction, gene expression, synaptic plasticity, signal transduction etc. but the significance of calcium oscillation is not yet completely understood in most of the cell types. A number of investigators have reported the oscillatory behavior of calcium due to intracellular concentration of inositol 1,4,5-trisphosphate (IP3). In this paper, an attempt has been made to study the oscillations induced in calcium due to dynamically changing membrane potential with special relevance to sodium pump. A mathematical model is developed which incorporates nearly all important and necessary biophysical components like L-type calcium channel, sodium channel, potassium channel, cytosolic buffers, calcium pump, sodium–calcium exchanger (NCX), sodium–potassium ATPase (sodium pump), and dynamic membrane potential. These channels have realistic gating mechanism and emulate the gating mechanism proposed in the famous paper of Hodgkin and Huxley.1 The model leads to an initial value problem involving system of non-linear ordinary differential equations. A numerical solution has been obtained using Gear's method. The numerical results have been used to study the effect of sodium pump over the frequency of Ca 2+ oscillation. At lower and higher sodium pump current densities the Ca 2+ oscillation frequency is observed to be 278 Hz and 225 Hz respectively.

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28

Amran, M. S., N. Homma e K. Hashimoto. "Effects of SEA0400 on Ouabain-induced Arrhythmias in Guinea Pigs". Journal of Scientific Research 4, n. 1 (26 dicembre 2011): 213. http://dx.doi.org/10.3329/jsr.v4i1.7722.

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Abstract (sommario):

The sodium-calcium exchange (NCX) is one of the major regulators of intracellular Ca2+ concentration in cardiac myocytes. The effects of NCX blockers as antiarrhythmic agents are still controversial. We investigated antiarrhythmic effects of SEA0400 (SEA), a novel NCX inhibitor, on ouabain-induced arrhythmias in guinea pigs. In the whole animal arrhythmia model, we observed effects of SEA on the ouabain-induced arrhythmia using ECG recordings. In the isolated myocyte, we observed action potential configurations and oscillations due to calcium overload using the current clamp method. In the whole animal model, SEA at a dose range of 1-10 mg/kg (intravenous, bolus) suppressed ouabain-induced arrhythmias dose-dependently. In isolated ventricular myocytes, SEA (0.1-3 µM) suppressed ouabain-induced oscillatory activity observed between action potentials. SEA (0.1-3 µM) also suppressed ouabain-induced NCX current (INCX) that is also called transient inward current (ITI). Our results indicate that NCX is involved in arrhythmia and oscillatory activity induced by ouabain. The inhibition of these arrhythmias and oscillatory activity by SEA might result from the inhibition of NCX.Keywords: Na+-Ca2+ exchange (NCX); SEA0400; NCX inhibitors; current clamp; ECG.© 2012 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v4i1.7722J. Sci. Res. 4 (1), 213-225 (2012)

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29

Barthmes, Maria, Jun Liao, Youxing Jiang, Andrea Brüggemann e Christian Wahl-Schott. "Electrophysiological characterization of the archaeal transporter NCX_Mj using solid supported membrane technology". Journal of General Physiology 147, n. 6 (30 maggio 2016): 485–96. http://dx.doi.org/10.1085/jgp.201611587.

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Abstract (sommario):

Sodium–calcium exchangers (NCXs) are membrane transporters that play an important role in Ca2+ homeostasis and Ca2+ signaling. The recent crystal structure of NCX_Mj, a member of the NCX family from the archaebacterium Methanococcus jannaschii, provided insight into the atomistic details of sodium–calcium exchange. Here, we extend these findings by providing detailed functional data on purified NCX_Mj using solid supported membrane (SSM)–based electrophysiology, a powerful but unexploited tool for functional studies of electrogenic transporter proteins. We show that NCX_Mj is highly selective for Na+, whereas Ca2+ can be replaced by Mg2+ and Sr2+ and that NCX_Mj can be inhibited by divalent ions, particularly Cd2+. By directly comparing the apparent affinities of Na+ and Ca2+ for NCX_Mj with those for human NCX1, we show excellent agreement, indicating a strong functional similarity between NCX_Mj and its eukaryotic isoforms. We also provide detailed instructions to facilitate the adaption of this method to other electrogenic transporter proteins. Our findings demonstrate that NCX_Mj can serve as a model for the NCX family and highlight several possible applications for SSM-based electrophysiology.

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30

Estacion, M., B. P. S. Vohra, S. Liu, J. Hoeijmakers, C. G. Faber, I. S. J. Merkies, G. Lauria, J. A. Black e S. G. Waxman. "Ca2+ toxicity due to reverse Na+/Ca2+ exchange contributes to degeneration of neurites of DRG neurons induced by a neuropathy-associated Nav1.7 mutation". Journal of Neurophysiology 114, n. 3 (settembre 2015): 1554–64. http://dx.doi.org/10.1152/jn.00195.2015.

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Abstract (sommario):

Gain-of-function missense mutations in voltage-gated sodium channel Nav1.7 have been linked to small-fiber neuropathy, which is characterized by burning pain, dysautonomia and a loss of intraepidermal nerve fibers. However, the mechanistic cascades linking Nav1.7 mutations to axonal degeneration are incompletely understood. The G856D mutation in Nav1.7 produces robust changes in channel biophysical properties, including hyperpolarized activation, depolarized inactivation, and enhanced ramp and persistent currents, which contribute to the hyperexcitability exhibited by neurons containing Nav1.8. We report here that cell bodies and neurites of dorsal root ganglion (DRG) neurons transfected with G856D display increased levels of intracellular Na+ concentration ([Na+]) and intracellular [Ca2+] following stimulation with high [K+] compared with wild-type (WT) Nav1.7-expressing neurons. Blockade of reverse mode of the sodium/calcium exchanger (NCX) or of sodium channels attenuates [Ca2+] transients evoked by high [K+] in G856D-expressing DRG cell bodies and neurites. We also show that treatment of WT or G856D-expressing neurites with high [K+] or 2-deoxyglucose (2-DG) does not elicit degeneration of these neurites, but that high [K+] and 2-DG in combination evokes degeneration of G856D neurites but not WT neurites. Our results also demonstrate that 0 Ca2+ or blockade of reverse mode of NCX protects G856D-expressing neurites from degeneration when exposed to high [K+] and 2-DG. These results point to [Na+] overload in DRG neurons expressing mutant G856D Nav1.7, which triggers reverse mode of NCX and contributes to Ca2+ toxicity, and suggest subtype-specific blockade of Nav1.7 or inhibition of reverse NCX as strategies that might slow or prevent axon degeneration in small-fiber neuropathy.

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31

Moonga, Baljit S., Robert Davidson, Li Sun, Olugbenga A. Adebanjo, James Moser, Mohammad Abedin, Neeha Zaidi, Christopher L. H. Huang e Mone Zaidi. "Identification and Characterization of a Sodium/Calcium Exchanger, NCX-1, in Osteoclasts and Its Role in Bone Resorption". Biochemical and Biophysical Research Communications 283, n. 4 (maggio 2001): 770–75. http://dx.doi.org/10.1006/bbrc.2001.4870.

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32

Khananshvili, Daniel. "Sodium-calcium exchangers (NCX): molecular hallmarks underlying the tissue-specific and systemic functions". Pflügers Archiv - European Journal of Physiology 466, n. 1 (27 novembre 2013): 43–60. http://dx.doi.org/10.1007/s00424-013-1405-y.

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33

Moon, H. S., E. Choi e C. Hyun. "The Cardiac Sodium-Calcium Exchanger Gene (NCX-1) is a Potential Canine Cardiac Biomarker of Chronic Mitral Valvular Insufficiency". Journal of Veterinary Internal Medicine 22, n. 6 (novembre 2008): 1360–65. http://dx.doi.org/10.1111/j.1939-1676.2008.0209.x.

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34

Hassan, Mohamed Tarek, e Jonathan Lytton. "Potassium-dependent sodium-calcium exchanger (NCKX) isoforms and neuronal function". Cell Calcium 86 (marzo 2020): 102135. http://dx.doi.org/10.1016/j.ceca.2019.102135.

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35

Manunta, Paolo, Bruce P. Hamilton e John M. Hamlyn. "Salt intake and depletion increase circulating levels of endogenous ouabain in normal men". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 290, n. 3 (marzo 2006): R553—R559. http://dx.doi.org/10.1152/ajpregu.00648.2005.

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Abstract (sommario):

High-salt diets elevate circulating Na+ pump inhibitors, vascular resistance, and blood pressure. Ouabain induces a form of hypertension mediated via the α2-Na+ pump isoform and the calcium influx mode of the vascular sodium calcium exchanger (NCX). Whereas elevated levels of an endogenous ouabain (EO) and NCX have been implicated in salt-sensitive hypertension, acute changes in sodium balance do not affect plasma EO. This study investigated the impact of longer-term alterations in sodium balance on the circulating levels and renal clearance of EO in normal humans. Thirteen normal men consumed a normal diet, high-salt diet, and hydrochlorothiazide (HCTZ), each for 5-day periods to alter sodium balance. EO and other humoral and urinary variables were determined daily. On a normal diet, urinary sodium excretion (140 ± 16 meq/day), plasma EO (0.43 ± 0.08 nmol/l) and urinary EO excretion (1.04 ± 0.13 nmol/day) were at steady state. On the 3rd day of a high-salt diet, urine sodium excretion (315 ± 28 meq/day), plasma EO (5.8 ± 2.2 nmol/l), and the urinary EO excretion (1.69 ± 0.27 nmol/day) were significantly increased, while plasma renin activity and aldosterone levels were suppressed. The salt-evoked increase in plasma EO was greater in older individuals, in subjects whose baseline circulating EO was higher, and in those with low renal clearance. During HCTZ, body weight decreased and plasma renin activity, aldosterone, and EO (1.71 ± 0.77 nmol/l) rose, while urinary EO excretion remained within the normal range (1.44 ± 0.31 nmol/day). Blood pressure fell in one subject during HCTZ. HPLC of the plasma extracts showed one primary peak of EO immunoreactivity with a retention time equivalent to ouabain. High-salt diets and HCTZ raise plasma EO by stimulating EO secretion, and a J-shaped curve relates sodium balance and EO in healthy men. Under normal dietary conditions, ∼98% of the filtered load of EO is reabsorbed by the kidney, and differences in the circulating levels of EO are strongly influenced by secretion and urinary excretion of EO. The dramatic impact of high-salt diets on plasma EO is consistent with its proposed role as a humoral vasoconstrictor that links salt intake with vascular function in hypertension.

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36

Pallafacchina, Giorgia, Sofia Zanin e Rosario Rizzuto. "Recent advances in the molecular mechanism of mitochondrial calcium uptake". F1000Research 7 (28 novembre 2018): 1858. http://dx.doi.org/10.12688/f1000research.15723.1.

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Abstract (sommario):

In the last few decades, a large body of experimental evidence has highlighted the complex role for mitochondria in eukaryotic cells: they are not only the site of aerobic metabolism (thus providing most of the ATP supply for endergonic processes) but also a crucial checkpoint of cell death processes (both necrosis and apoptosis) and autophagy. For this purpose, mitochondria must receive and decode the wide variety of physiological and pathological stimuli impacting on the cell. The “old” notion that mitochondria possess a sophisticated machinery for accumulating and releasing Ca2+, the most common and versatile second messenger of eukaryotic cells, is thus no surprise. What may be surprising is that the identification of the molecules involved in mitochondrial Ca2+ transport occurred only in the last decade for both the influx (the mitochondrial Ca2+ uniporter, MCU) and the efflux (the sodium calcium exchanger, NCX) pathways. In this review, we will focus on the description of the amazing molecular complexity of the MCU complex, highlighting the numerous functional implications of the tissue-specific expression of the variants of the channel pore components (MCU/MCUb) and of the associated proteins (MICU 1, 2, and 3, EMRE, and MCUR1).

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37

Zhang, Weihua, Changqing Xu, Guangdong Yang, Lingyun Wu e Rui Wang. "Interaction of H2S with Calcium Permeable Channels and Transporters". Oxidative Medicine and Cellular Longevity 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/323269.

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Abstract (sommario):

A growing amount of evidence has suggested that hydrogen sulfide (H2S), as a gasotransmitter, is involved in intensive physiological and pathological processes. More and more research groups have found that H2S mediates diverse cellular biological functions related to regulating intracellular calcium concentration. These groups have demonstrated the reciprocal interaction between H2S and calcium ion channels and transporters, such as L-type calcium channels (LTCC), T-type calcium channels (TTCC), sodium/calcium exchangers (NCX), transient receptor potential (TRP) channels,β-adrenergic receptors, and N-methyl-D-aspartate receptors (NMDAR) in different cells. However, the understanding of the molecular targets and mechanisms is incomplete. Recently, some research groups demonstrated that H2S modulates the activity of calcium ion channels through protein S-sulfhydration and polysulfide reactions. In this review, we elucidate that H2S controls intracellular calcium homeostasis and the underlying mechanisms.

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38

Lariccia, Vincenzo, Silvia Piccirillo, Alessandra Preziuso, Salvatore Amoroso e Simona Magi. "Cracking the code of sodium/calcium exchanger (NCX) gating: Old and new complexities surfacing from the deep web of secondary regulations". Cell Calcium 87 (maggio 2020): 102169. http://dx.doi.org/10.1016/j.ceca.2020.102169.

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39

Smith, L., H. Porzig, H. W. Lee e J. B. Smith. "Phorbol esters downregulate expression of the sodium/calcium exchanger in renal epithelial cells". American Journal of Physiology-Cell Physiology 269, n. 2 (1 agosto 1995): C457—C463. http://dx.doi.org/10.1152/ajpcell.1995.269.2.c457.

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Abstract (sommario):

The Na+/Ca2+ exchanger (NCE) contributes to Ca2+ reabsorption by connecting tubules of the nephron. A line of renal epithelial cells from monkey kidney (LLC-MK2) was used to investigate the regulation of NCE expression. After the activation of protein kinase C (PKC) by phorbol myristate acetate (PMA), NCE activity decreased exponentially by 75% in 48 h (half time approximately 19 h). PMA decreased NCE mRNA by 85% in 24 h. The decrease in NCE transcript preceded the downregulation of NCE activity. NCE protein was quantified with a monoclonal antibody to cardiac NCE. PMA decreased the binding of 3H-labeled antibody to cell sonicates by 40% in 24 h. Immunoblots show that PMA produced a marked and extended increase in membrane-associated PKC-alpha, although PMA depleted total PKC-alpha by 65% in 24 h. In vivo 32P labeling of myristolated alanine-rich C kinase substrate, a specific PKC substrate, confirmed that PMA produced a rapid and extended activation of PKC. 4 alpha-PMA, a stereoisomer of PMA that neither binds nor activates PKC, had no effect on NCE activity or transcript. These findings indicate that activation of PKC with phorbol esters downregulates NCE mRNA, protein, and activity in renal epithelial cells.

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40

Groenke, Sabine, Eric D. Larson, Haruko Nakano, Atsushi Nakano, Catherine Proenza, Kenneth D. Philipson e Joshua I. Goldhaber. "Atrial-Specific NCX KO Mice Reveal Dependence of Sinoatrial Node Pacemaker Activity on Sodium-Calcium Exchange". Biophysical Journal 102, n. 3 (gennaio 2012): 663a. http://dx.doi.org/10.1016/j.bpj.2011.11.3612.

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41

Cantero-Recasens, Gerard, Cristian M. Butnaru, Nathalie Brouwers, Sandra Mitrovic, Miguel A. Valverde e Vivek Malhotra. "Sodium channel TRPM4 and sodium/calcium exchangers (NCX) cooperate in the control of Ca2+-induced mucin secretion from goblet cells". Journal of Biological Chemistry 294, n. 3 (27 novembre 2018): 816–26. http://dx.doi.org/10.1074/jbc.ra117.000848.

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42

Khananshvili, Daniel. "The SLC8 gene family of sodium–calcium exchangers (NCX) – Structure, function, and regulation in health and disease". Molecular Aspects of Medicine 34, n. 2-3 (aprile 2013): 220–35. http://dx.doi.org/10.1016/j.mam.2012.07.003.

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43

Nam, S. J., S. H. Han, H. W. Kim e C. Hyun. "The Cardiac Biomarker Sodium-Calcium Exchanger (NCX-1) Can Differentiate between Heart Failure and Renal Failure: A Comparative Study of NCX-1 Expression in Dogs with Chronic Mitral Valvular Insufficiency and Azotemia". Journal of Veterinary Internal Medicine 24, n. 6 (novembre 2010): 1383–87. http://dx.doi.org/10.1111/j.1939-1676.2010.0628.x.

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44

Liu, Cuiping, Guoli Shao, Yirong Lu, Minmin Xue, Fenfen Liang, Zhenshu Zhang e Lan Bai. "Parathyroid Hormone-Related Protein (1-40) Enhances Calcium Uptake in Rat Enterocytes Through PTHR1 Receptor and Protein Kinase Cα/β Signaling". Cellular Physiology and Biochemistry 51, n. 4 (2018): 1695–709. http://dx.doi.org/10.1159/000495674.

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Abstract (sommario):

Background/Aims: Parathyroid hormone-related protein (PTHrP) is implicated in regulating calcium homeostasis in vertebrates, including sea bream, chick, and mammals. However, the molecular mechanism underlying the function of PTHrP in regulating calcium transport is still not fully investigated. This study aimed to investigate the effect of PTHrP on the calcium uptake and its underlying molecular mechanism in rat enterocytes. Methods: The rat intestinal epithelial cell line (IEC-6) was used. Calcium uptake was determined by using the fluo-4 acetoxymethyl ester fluorescence method. The expression levels of RNAs and proteins was assessed by RT-PCR and Western-blot, respectively. Results: PTHrP (1-40) induced rapid calcium uptake in enterocytes in a dose-dependent manner. PTHrP (1-40) up-regulated parathyroid hormone 1 receptor (PTHR1) protein but not 1,25D3-MARRS receptor. Pre-treatment of anti- PTHR1 antibody abolished the PTHrP (1-40)-induced calcium uptake. PTHrP (1-40) significantly up-regulated four transcellular calcium transporter proteins, potential vanilloid member 6 (TRPV6), calbindin-D9k (CaBP-D9k), sodium-calcium exchanger 1 (NCX1) and plasma membrane calcium ATPase 1 (PMCA1), in a dose- and time-dependent manner. Pre-treatment with TRPV6 or CaBP-D9k antibodies or knockout of rat TRPV6 or CaBP-D9k markedly inhibited PTHrP (1-40)-induced calcium uptake, whereas inhibition of NCX or PMCA1 by antibodies or inhibitors had no effect on PTHrP(1-40)-induced calcium uptake. Furthermore, PTHrP (1-40) treatment up-regulated protein levels of protein kinase C (PKC α/β) and protein kinase A (PKA). Pretreatment of PKC α/β inhibitor (but not PKA inhibitor) inhibited PTHrP (1-40)-induced calcium uptake. Conclusion: PTHrP (1-40) stimulates calcium uptake via PTHR1 receptor and PKC α/β signaling pathway in rat enterocytes, and calcium transporters TRPV6 and CaBP-D9k are necessary for this stimulatory effect.

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Morales, Danna, Tamara Hermosilla e Diego Varela. "Calcium-dependent inactivation controls cardiac L-type Ca2+ currents under β-adrenergic stimulation". Journal of General Physiology 151, n. 6 (27 febbraio 2019): 786–97. http://dx.doi.org/10.1085/jgp.201812236.

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Abstract (sommario):

The activity of L-type calcium channels is associated with the duration of the plateau phase of the cardiac action potential (AP) and it is controlled by voltage- and calcium-dependent inactivation (VDI and CDI, respectively). During β-adrenergic stimulation, an increase in the L-type current and parallel changes in VDI and CDI are observed during square pulses stimulation; however, how these modifications impact calcium currents during an AP remains controversial. Here, we examined the role of both inactivation processes on the L-type calcium current activity in newborn rat cardiomyocytes in control conditions and after stimulation with the β-adrenergic agonist isoproterenol. Our approach combines a self-AP clamp (sAP-Clamp) with the independent inhibition of VDI or CDI (by overexpressing CaVβ2a or calmodulin mutants, respectively) to directly record the L-type calcium current during the cardiac AP. We find that at room temperature (20–23°C) and in the absence of β-adrenergic stimulation, the L-type current recapitulates the AP kinetics. Furthermore, under our experimental setting, the activity of the sodium–calcium exchanger (NCX) does not affect the shape of the AP. We find that hindering either VDI or CDI prolongs the L-type current and the AP in parallel, suggesting that both inactivation processes modulate the L-type current during the AP. In the presence of isoproterenol, wild-type and VDI-inhibited cardiomyocytes display mismatched L-type calcium current with respect to their AP. In contrast, CDI-impaired cells maintain L-type current with kinetics similar to its AP, demonstrating that calcium-dependent inactivation governs L-type current kinetics during β-adrenergic stimulation.

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46

Kohajda, Zsófia, Nikolett Farkas-Morvay, Norbert Jost, Norbert Nagy, Amir Geramipour, András Horváth, Richárd S. Varga et al. "The Effect of a Novel Highly Selective Inhibitor of the Sodium/Calcium Exchanger (NCX) on Cardiac Arrhythmias in In Vitro and In Vivo Experiments". PLOS ONE 11, n. 11 (10 novembre 2016): e0166041. http://dx.doi.org/10.1371/journal.pone.0166041.

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47

Dave, Vijay, e Rohit Manchanda. "A computational model of the Ca2+ transients and influence of buffering in guinea pig urinary bladder smooth muscle cells". Journal of Bioinformatics and Computational Biology 15, n. 03 (20 aprile 2017): 1750011. http://dx.doi.org/10.1142/s0219720017500111.

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Abstract (sommario):

Many cellular events including electrical activity and muscle contraction are regulated and coordinated by intracellular [Formula: see text] concentration ([[Formula: see text]][Formula: see text]. In detrusor smooth muscle (DSM) cells, [[Formula: see text]]i is normally maintained at very low levels and rises transiently during signalling processes as a result of (i) influx from the extracellular space (mainly via L-type and T-type [Formula: see text] channels) and (ii) [Formula: see text] release from sarcoplasmic reticulum (SR) into the cytoplasm. Intracellular [Formula: see text] buffers, both fixed and diffusible, play a vital role in shaping the radial distribution of free [Formula: see text]. Our aim, in the work presented here, is to develop a mathematical model of [Formula: see text] buffering and diffusion and to generate [Formula: see text] transient in guinea pig DSM cells. The [Formula: see text] transient is generated using inward [Formula: see text] current that arises following voltage clamp and mediated by L-type and T-type [Formula: see text] channels. [Formula: see text] transient is obtained for different radial locations (or shells) of the DSM cytosol. This modeling study explores the levels of [[Formula: see text]]i achieved near the plasma membrane and in deeper locations. The [Formula: see text] transient generated in our model shows a high degree of similarity with experimental findings in terms of amplitude, duration and half-decay time. A number of different buffer properties such as concentration and mobility are tested for their effect on amplitude and shape of [Formula: see text] transient. The presence of fast buffer concentration in the cytosol markedly delays the rise of [[Formula: see text]]i in the core of the cell. Increase in the mobility of fast buffer slightly speeds up the redistribution of [Formula: see text]. To explore the model further, the role of plasma membrane [Formula: see text]-ATPase (PMCA) pump, sarcoplasmic/endoplasmic reticulum [Formula: see text]-ATPase (SERCA) pump and sodium calcium exchanger (NCX) on [Formula: see text] transient is studied and it is suggested that NCX may be of primary importance for the immediate lowering of [[Formula: see text]]i during the falling phase of a [Formula: see text] transient in DSM cells.

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48

Sobrinho, Cleyton R., Christopher M. Gonçalves, Ana C. Takakura, Daniel K. Mulkey e Thiago S. Moreira. "Fluorocitrate-mediated depolarization of astrocytes in the retrotrapezoid nucleus stimulates breathing". Journal of Neurophysiology 118, n. 3 (1 settembre 2017): 1690–97. http://dx.doi.org/10.1152/jn.00032.2017.

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Evidence indicates that CO2/H+-evoked ATP released from retrotrapezoid nucleus (RTN) astrocytes modulates the activity of CO2-sensitive neurons. RTN astrocytes also sense H+ by inhibition of Kir4.1 channels; however, the relevance of this pH-sensitive current remains unclear since ATP release appears to involve CO2-dependent gating of connexin 26 hemichannels. Considering that depolarization mediated by H+ inhibition of Kir4.1 channels is expected to increase sodium bicarbonate cotransporter (NBC) conductance and favor Ca2+ influx via the sodium calcium exchanger (NCX), we hypothesize that depolarization in the presence of CO2 is sufficient to facilitate ATP release and enhance respiratory output. Here, we confirmed that acute exposure to fluorocitrate (FCt) reversibly depolarizes RTN astrocytes and increased activity of RTN neurons by a purinergic-dependent mechanism. We then made unilateral injections of FCt into the RTN or two other putative chemoreceptor regions (NTS and medullary raphe) to depolarize astrocytes under control conditions and during P2-recepetor blockade while measuring cardiorespiratory activities in urethane-anesthetized, vagotomized, artificially ventilated male Wistar rats. Unilateral injection of FCt into the RTN increased phrenic (PNA) amplitude and frequency without changes in arterial pressure. Unilateral injection of pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonate (PPADS, a P2-receptor antagonist) into the RTN dampened both PNA amplitude and frequency responses to FCt. Injection of MRS2179 (P2Y1-receptor antagonist) into the RTN did not affect the FCt-induced respiratory responses. Fluorocitrate had no effect on breathing when injected into the NTS or raphe. These results suggest that depolarization can facilitate purinergic enhancement of respiratory drive from the RTN. NEW & NOTEWORTHY Astrocytes in the retrotrapezoid nucleus (RTN) are known to function as respiratory chemoreceptors; however, it is not clear whether changes in voltage contribute to astrocyte chemoreception. We showed that depolarization of RTN astrocytes at constant CO2 levels is sufficient to modulate RTN chemoreception by a purinergic-dependent mechanism. These results support the possibility that astrocyte depolarization can facilitate purinergic enhancement of respiratory drive from the RTN.

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49

Schoenmakers, T. J., e G. Flik. "Sodium-extruding and calcium-extruding sodium/calcium exchangers display similar calcium affinities". Journal of Experimental Biology 168, n. 1 (1 luglio 1992): 151–59. http://dx.doi.org/10.1242/jeb.168.1.151.

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Na+/Ca2+ exchange activities in purely inside-out and mixed inside-out and right-side-out fish enterocyte basolateral plasma membrane vesicle preparations display equal affinities for Ca2+, showing that only the intracellular Ca2+ transport site of the Na+/Ca2+ exchanger is detected in experiments on vesicle preparations with mixed orientation. Therefore, Ca2+ pump and Na+/Ca2+ exchange activity may be compared directly without correction for vesicle orientation. The Na+/Ca2+ exchange activity in fish enterocyte vesicles is compared to the activity found in dog erythrocyte vesicles. The calcium-extruding exchanger in fish basolateral plasma membranes shows values of Km and V(max) for calcium similar to those found for the sodium-extruding exchanger in dog erythrocyte membranes, indicating that differences in electrochemical gradients underlie the difference in cellular function of the two exchangers.

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50

Pittner, János, Kristie Rhinehart e Thomas L. Pallone. "Ouabain modulation of endothelial calcium signaling in descending vasa recta". American Journal of Physiology-Renal Physiology 291, n. 4 (ottobre 2006): F761—F769. http://dx.doi.org/10.1152/ajprenal.00326.2005.

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Using fura 2-loaded vessels, we tested whether ouabain modulates endothelial cytoplasmic calcium concentration ([Ca2+]CYT) in rat descending vasa recta (DVR). Over a broad range between 10−10 and 10−4 M, ouabain elicited biphasic peak and plateau [Ca2+]CYT elevations. Blockade of voltage-gated Ca2+ entry with nifedipine did not affect the response to ouabain mitigating against a role for myo-endothelial gap junctions. Reduction of extracellular Na+ concentration ([Na+]o) or Na+/Ca2+ exchanger (NCX) inhibition with SEA-0400 (10−6 M) elevated [Ca2+]CYT, supporting a role for NCX in the setting of basal [Ca2+]CYT. SEA-0400 abolished the [Ca2+]CYT response to ouabain implicating NCX as a mediator. The transient peak phase of [Ca2+]CYT elevation that followed either ouabain or reduction of [Na+]o was abolished by 2-aminoethoxydiphenyl borate (5 × 10−5 M). Cation channel blockade with La3+ (10 μM) or SKF-96365 (10 μM) also attenuated the ouabain-induced [Ca2+]CYT response. Ouabain pretreatment increased the [Ca2+]CYT elevation elicited by bradykinin (10−7 M). We conclude that inhibition of ouabain-sensitive Na+-K+-ATPase enhances DVR endothelial Ca2+ store loading and modulates [Ca2+]CYT signaling through mechanisms that involve NCX, Ca2+ release, and cation channel activation.

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