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1.
Genistein inhibits the inward rectifying potassium current in guinea pig ventricular myocytes 总被引:3,自引:0,他引:3
Genistein is an isoflavone with potent inhibitory activity on protein tyrosine kinase. Previous studies have shown that genistein has additional effects, among which the direct blocking effects on various ionic channels have recently been disclosed. Using whole-cell voltage clamp and current clamp techniques, we demonstrate that micromolar concentrations of genistein dose-dependently and reversibly inhibit the inward rectifying K(+) current, and depolarize the resting membrane potential, resulting in abnormal automaticity in guinea pig ventricular myocytes. Interestingly, another potent tyrosine kinase inhibitor, tyrphostin 51, did not produce the same inhibitory effect, while the inactive analogue of genistein, daidzein, had a similar blocking effect. We suggest that genistein directly blocks the inward rectifying K(+) current in ventricular myocytes, and one should be cautious of its pro-arrhythmic effect in clinical use. 相似文献
2.
Mutoh H Yoshino M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(1):21-28
The Ca2+-conducting pathway of myocytes isolated from the cricket lateral oviduct was investigated by means of the whole-cell patch clamp technique. In voltage-clamp configuration, two types of whole cell inward currents were identified. One was voltage-dependent, initially activated at –40 mV and reaching a maximum at 10 mV with the use of 140 mM Cs2+-aspartate in the patch pipette and normal saline in the bath solution. Replacement of the external Ca2+ with Ba2+ slowed the current decay. Increasing the external Ca2+ or Ba2+ concentration increased the amplitude of the inward current and the current–voltage (I–V) relationship was shifted as expected from a screening effect on negative surface charges. The inward current could be carried by Na+ in the absence of extracellular Ca2+. Current carried by Na+ (I
Na) was almost completely blocked by the dihydropyridine Ca2+ channel antagonist, nifedipine, suggesting that the I
Na is through voltage-dependent L-type Ca2+ channels. The other inward current is voltage-independent and its I–V relationship was linear between –100 mV to 0 mV with a slight inward rectification at more hyperpolarizing membrane potentials when 140 mM Cs+-aspartate and 140 mM Na+-gluconate were used in the patch pipette and in the bath solution, respectively. A similar current was observed even when the external Na+ was replaced with an equimolar amount of K+ or Cs+, or 50 mM Ca2+ or Ba2+. When the osmolarity of the bath solution was reduced by removing mannitol from the bath solution, the inward current became larger at negative potentials. The I–V relationship for the current evoked by the hypotonic solution also showed a linear relationship between –100 mV to 0 mV. Bath application of Gd3+ (10 M) decreased the inward current activated by membrane hyperpolarization. These results clearly indicate that the majority of current activated by a membrane hyperpolarization is through a stretch-activated Ca2+-permeable nonselective cation channel (NSCC). Here, for the first time, we have identified voltage-dependent L-type Ca2+ channel and stretch-activated Ca2+-permeable NSCCs from enzymatically isolated muscle cells of the cricket using the whole-cell patch clamp recording technique.Abbreviations
I
Ca
Ca2+ current
-
I
Na
Na+ current
-
I–V
current–voltage
-
NSCC
nonselective cation channel
Communicated by G. Heldmaier 相似文献
3.
Zorn-Pauly K Schaffer P Pelzmann B Bernhart E Lang P Koidl B 《Physiological research / Academia Scientiarum Bohemoslovaca》2004,53(4):369-377
The aim of this investigation was to study L-type and T-type Ca(2+) current (I(CaL) and I(CaT)) in short-term cultured adult guinea pig ventricular myocytes. The isolated myocytes were suspended in serum-supplemented medium up to 5 days. Using whole-cell patch clamp techniques ICaL and ICaT were studied by applying voltage protocols from different holding potentials (-40 and -90 mV). After 5 days in culture the myocytes still showed their typical rod shaped morphology but a decline in cell membrane capacitance (26 %). The peak density of ICaT was reduced significantly between day 0 (-1.6+/-0.37 pA/pF, n=9) and day 5 (-0.4+/-0.13 pA/pF, n=11), whereas peak ICaL density revealed no significant differences during culturing. The I(CaT)/I(CaL) ratio dropped from 0.13 at day 0 to 0.05 at day 5. Compared with day 0 I(CaL) the steady state inactivation curve of day 1, day 3 and day 5 myocytes was slightly shifted to more negative potentials. Our data indicate that guinea pig ventricular L-type and T-type Ca(2+) channels are differently regulated in culture. 相似文献
4.
Numata T Yoshino M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(4):257-263
The single Ca2+ channel activity was obtained from cell-attached patch recordings with the use of pipettes filled with 100 mM Ba2+ as the charge carrier in myocytes isolated from the lateral oviduct of cricket Gryllus bimaculatus. The following results were obtained. (1) The channel had a unitary conductance of 18 pS. (2) The open time histogram of the channel could be fitted with a single exponential while the closed time histogram could be fitted with the sum of two exponentials, suggesting that there are at least one open state and two closed states for this channel. (3) The open probability of the channel increased with increasing membrane depolarization. (4) The mean current reconstructed by averaging individual current trace responses inactivated slowly and the current–voltage relationship for the peak mean current showed a bell-shaped relation. (5) The dihydropyridine (DHP) Ca2+ antagonist, nifedipine, reduced the mean current by increasing the proportion of blank sweeps. On the other hand, the DHP Ca2+ agonist, Bay K 8644, increased the mean current by increasing the mean open-times of the channel. These results confirm a presence of DHP-sensitive L-type Ca2+ channel in myocytes isolated from the lateral oviduct of cricket G. bimaculatus. 相似文献
5.
The clustering of cardiac RyR mutations, linked to sudden cardiac death (SCD), into several regions in the amino acid sequence
underlies the hypothesis that these mutations interfere with stabilising interactions between different domains of the RyR2.
SCD mutations cause increased channel sensitivity to cytoplasmic and luminal Ca2+. A synthetic peptide corresponding to part of the central domain (DPc10:2460G–P2495) was designed to destabilise the interaction of the N-terminal and central domains of wild-type RyR2 and mimic the effects
of SCD mutations. With Ca2+ as the sole regulating ion, DPc10 caused increased channel activity which could be reversed by removal of the peptide whereas
in the presence of ATP DPc10 caused no activation. In support of the domain destablising hypothesis, the corresponding peptide
(DPc10-mut) containing the CPVT mutation R2474S did not affect channel activity under any circumstances. DPc10-induced activation
was due to a small increase in RyR2 sensitivity to cytoplasmic Ca2+ and a large increase in the magnitude of luminal Ca2+ activation. The increase in the luminal Ca2+ response appeared reliant on the luminal-to-cytoplasmic Ca2+ flux in the channel, indicating that luminal Ca2+ was activating the RyR2 via its cytoplasmic Ca2+ sites. DPc10 had no significant effect on the RyR2 gating associated with luminal Ca2+ sensing sites. The results were fitted by the luminal-triggered Ca2+ feed-through model and the effects of DPc10 were explained entirely by perturbations in cytoplasmic Ca2+-activation mechanism. 相似文献
6.
Daniel C. Moreira-Lobo Jader S. Cruz Flavia R. Silva Fabíola M. Ribeiro Christopher Kushmerick Fernando A. Oliveira 《Cellular and molecular neurobiology》2017,37(3):453-460
Thiamine (vitamin B1) is co-factor for three pivotal enzymes for glycolytic metabolism: pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase. Thiamine deficiency leads to neurodegeneration of several brain regions, especially the cerebellum. In addition, several neurodegenerative diseases are associated with impairments of glycolytic metabolism, including Alzheimer’s disease. Therefore, understanding the link between dysfunction of the glycolytic pathway and neuronal death will be an important step to comprehend the mechanism and progression of neuronal degeneration as well as the development of new treatment for neurodegenerative states. Here, using an in vitro model to study the effects of thiamine deficiency on cerebellum granule neurons, we show an increase in Ca2+ current density and CaV1.2 expression. These results indicate a link between alterations in glycolytic metabolism and changes to Ca2+ dynamics, two factors that have been implicated in neurodegeneration. 相似文献
7.
The basic mechanisms of regulation of Ca2+ influx have been studied in murine myoblasts proliferating and differentiating in culture. The presence of L-type Ca2+ channels in proliferating myoblasts is shown for the first time. It is also shown that the influx of Ca2+ through these channels is regulated by the adrenergic system. The influx of Ca2+ after activation of the adrenergic system by addition of adrenaline has been estimated in comparison with the contribution
of reticular stocks exhausted by ATP in calcium-free medium. The Ca2+ influx in proliferating myoblasts is regulated by β-2 adrenergic receptors whose action is mediated by adenylate cyclase
through L-type calcium channels. In differentiating myoblasts, the adrenaline-induced Ca2+ influx is substantially lower than in proliferating cells, and maximal influx of Ca2+ may be reached only upon exhaustion of reticular stocks. 相似文献
8.
Premkumar LS 《The Journal of membrane biology》2005,204(3):129-136
The primary target for cocaine is believed to be monoamine transporters because of cocaine’s high-affinity binding that prevents
re-uptake of released neurotransmitter. However, direct interaction with ion channels has been shown to be important for certain
pharmacological/toxicological effects of cocaine. Here I show that cocaine selectively blocks a calcium-dependent K+ channel in hippocampal neurons grown in culture (IC50 = ∼30 μM). Single-channel recordings show that in the presence of cocaine, the channel openings are interrupted with brief closures
(flicker block). As the concentration of cocaine is increased the open-time is reduced, whereas the duration of brief closures
is independent of concentration. The association and dissociation rate constants of cocaine for the neuronal Ca2+-activated K+ channels are 261 ± 37 μM−1s−1 and 11451 ± 1467 s−1. The equilibrium dissociation constant (KB) for cocaine, determined from single-channel parameters, is 43 μM. The lack of voltage dependence of block suggests that cocaine probably binds to a site at the mouth of the pore. Block of
Ca2+-dependent K+ channels by cocaine may be involved in functions that include broadening of the action potential, which would facilitate
transmitter release, enhancement of smooth muscle contraction particularly in blood vessels, and modulation of repetitive
neuronal firing by altering the repolarization and afterhyperpolarization phases of the action potential. 相似文献
9.
Cerella C Mearelli C Coppola S D'Alessio M De Nicola M Diederich M Ghibelli L 《Apoptosis : an international journal on programmed cell death》2007,12(12):2207-2219
The very early events of the intrinsic, damage-induced apoptotic pathway, i.e., upstream to Bax activation, probably consist
of physico-chemical alterations (i.e., redox, pH or Ca2+ changes) rather then subtle molecular interactions, and in spite of many studies they remain unclear. One problem is that
cells undergo apoptosis in an asynchronous way, leading to heterogeneity in the cell population that impairs the results of
bulk analyses. In this study, we present a flow cytometric approach for studying Ca2+ alteration in apoptosis at the single cell level. By means of a multiparametric analysis, we could discriminate different
sub-populations, i.e., viable and apoptotic cells and cells in secondary necrosis, and separately analyse static as well as
dynamic Ca2+ parameters in each sub-population. With this approach, we have identified a set of sequential Ca2+ changes; two very early ones occur prior to any other apoptotic alterations, whereas a later change coincides with the appearance
of apoptosis. Interestingly, the two pre-apoptotic changes occur simultaneously in all treated cells, i.e., at fixed times
post-treatment, whereas the later one occurs at varying times, i.e., within a wide time range, concomitantly with the other
apoptotic events. 相似文献
10.
Store-operated Ca2+ influx, suggested to be mediated via store-operated cation channel (SOC), is present in all cells. The molecular basis of SOC, and possible heterogeneity of these channels, are still a matter of controversy. Here we have compared the properties of SOC currents (I
SOC) in human submandibular glands cells (HSG) and human parotid gland cells (HSY) with I
CRAC (Ca2+ release-activated Ca2+ current) in RBL cells. Internal Ca2+ store-depletion with IP3 or thapsigargin activated cation channels in all three cell types. 1 μM Gd3+ blocked channel activity in all cells. Washout of Gd3+ induced partial recovery in HSY and HSG but not RBL cells. 2-APB reversibly inhibited the channels in all cells. I
CRAC
in RBL cells displayed strong inward rectification with E
rev(Ca) = >+90 mV and E
rev (Na) = +60 mV. I
SOC in HSG cells showed weaker rectification with E
rev(Ca) = +25 mV and E
rev(Na) = +10 mV. HSY cells displayed a linear current with E
rev = +5 mV, which was similar in Ca2+- or Na+-containing medium. pCa/pNa was >500, 40, and 4.6 while pCs /pNa was 0.1,1, and 1.3, for RBL, HSG, and HSY cells, respectively. Evidence for anomalous mole fraction behavior of Ca2+/Na+ permeation was obtained with RBL and HSG cells but not HSY cells. Additionally, channel inactivation with Ca2+ + Na+ or Na+ in the bath was different in the three cell types. In aggregate, these data demonstrate that distinct store-dependent cation currents are stimulated in RBL, HSG, and HSY cells. Importantly, these data suggest a molecular heterogeneity, and possibly cell-specific differences in the function, of these channels.This revised version was published online in June 2005 with a corrected cover date. 相似文献
11.
Supplementation with CaCl2·2H2O (50 mg l−1) or CuSO4·5H2O (10 mg l−1) improved mannitol production by Candida magnoliae by 14.5 and 18.6% (25 and 32 g/L), respectively. When used in combination, they acted synergistically: Ca2+ decreased the intracellular concentration of mannitol 30%, whereas Cu2+ increased the intracellular activity of mannitol dehydrogenase 1.6-times more than control. Ca2+ probably works by altering the permeability of cells to mannitol, whereas, Cu2+ increases the activity of an enzyme responsible for mannitol biosynthesis. 相似文献
12.
Mechanism of luminal Ca<Superscript>2+</Superscript> and Mg<Superscript>2+</Superscript> action on the vacuolar slowly activating channels 总被引:2,自引:0,他引:2
The non-selective slow vacuolar (SV) channel can dominate tonoplast conductance, making it necessary to tightly control its activity. Applying the patch-clamp technique to vacuoles from sugar beet (Beta vulgaris L.) taproots we studied the effect of divalent cations on the vacuolar side of the SV channel. Our results show that the SV channel has two independent binding sites for vacuolar divalent cations, (i) a less selective one, inside the channel pore, binding to which impedes channel conductance, and (ii) a Ca2+-selective one outside the membrane-spanning part of the channel protein, binding to which stabilizes the channels closed conformations. Vacuolar Ca2+ and Mg2+ almost indiscriminately blocked ion fluxes through the open channel pore, decreasing measured single-channel current amplitudes. This low-affinity block displays marked voltage dependence, characteristic of a permeable blocker. Vacuolar Ca2+—with a much higher affinity than Mg2+—slows down SV channel activation and shifts the voltage dependence to more (cytosol) positive potentials. A quantitative analysis results in a model that exactly describes the Ca2+-specific effects on the SV channel activation kinetics and voltage gating. According to this model, multiple (approximately three) divalent cations bind with a high affinity at the luminal interface of the membrane to the channel protein, favoring the occupancy of one of the SV channels closed states (C2). Transition to another closed state (C1) diminishes the effective number of bound cations, probably due to mutual repulsion, and channel opening is accompanied by a decrease of binding affinity. Hence, the open state (O) is destabilized with respect to the two closed states, C1 and C2, in the presence of Ca2+ at the vacuolar side. The specificity for Ca2+ compared to Mg2+ is explained in terms of different binding affinities for these cations. In this study we demonstrate that vacuolar Ca2+ is a crucial regulator to restrict SV channel activity to a physiologically meaningful range, which is less than 0.1% of maximum SV channel activity.Abbreviation SV Slow vacuolar 相似文献
13.
Effects of nanomolar concentration dihydroouabain on calcium current and intracellular calcium in guinea pig ventricular myocytes 总被引:2,自引:0,他引:2
The effects of nanomolar concentration of dihydroouabain (DHO) on L-type calcium current (ICa-L), TTX-sensitive calcium current (ICa(TTX)), and intracellular calcium concentration ([Ca2+]i) were investigated in guinea pig ventricular myocytes. The whole-cell patch-clamp technique was used to record ICa-L and ICa(TTX); [Ca2+]i was detected and recorded with the confocal microscopy. The nanomolar concentration of DHO increased the ICa-L, ICa(TTX), and [Ca2+]i, which could be partially inhibited by nisoldipine or TTX, but still appeared in the absence of extracellular K+ and Na+. These data suggest that DHO could increase [Ca2+]i in non-beating myocytes via stimulating the ICa-L and ICa(TTX), or perhaps triggering directly a release of intracellular calcium. 相似文献
14.
Kirti Dhingra Petra Fousková Goran Angelovski Martin E. Maier Nikos K. Logothetis Éva Tóth 《Journal of biological inorganic chemistry》2008,13(1):35-46
Two new bismacrocyclic Gd3+ chelates containing a specific Ca2+ binding site were synthesized as potential MRI contrast agents for the detection of Ca2+ concentration changes at the millimolar level in the extracellular space. In the ligands, the Ca2+-sensitive BAPTA-bisamide central part is separated from the DO3A macrocycles either by an ethylene (L1) or by a propylene (L2) unit [H4BAPTA is 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid; H3DO3A is 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid]. The sensitivity of the Gd3+ complexes towards Ca2+ and Mg2+ was studied by 1H relaxometric titrations. A maximum relaxivity increase of 15 and 10% was observed upon Ca2+ binding to Gd2L1 and Gd2L2, respectively, with a distinct selectivity of Gd2L1 towards Ca2+ compared with Mg2+. For Ca2+ binding, association constants of log K = 1.9 (Gd2L1) and log K = 2.7 (Gd2L2) were determined by relaxometry. Luminescence lifetime measurements and UV–vis spectrophotometry on the corresponding Eu3+ analogues proved that the complexes exist in the form of monohydrated and nonhydrated species; Ca2+ binding in the central part of the ligand induces the formation of the monohydrated state. The increasing hydration number
accounts for the relaxivity increase observed on Ca2+ addition. A 1H nuclear magnetic relaxation dispersion and 17O NMR study on Gd2L1 in the absence and in the presence of Ca2+ was performed to assess the microscopic parameters influencing relaxivity. On Ca2+ binding, the water exchange is slightly accelerated, which is likely related to the increased steric demand of the central
part leading to a destabilization of the Ln–water binding interaction.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Inesi G Hua S Xu C Ma H Seth M Prasad AM Sumbilla C 《Journal of bioenergetics and biomembranes》2005,37(6):365-368
The Ca2+ transport ATPase of intracellular membranes (SERCA) can be inhibited by a series of chemical compounds such as Thapsigargin
(TG), 2,5-di(tert-butyl)hydroquinone (DBHQ) and 1,3-dibromo-2,4,6-tris (methyl-isothio-uronium) benzene (Br2-TITU). These compounds have specific binding sites in the ATPase protein, and different mechanisms of inhibition. On the
other hand, SERCA gene silencing offers a convenient and specific method for suppression of SERCA activity in cells. The physiological
and pharmacological implications of SERCA inhibition are discussed. 相似文献
16.
Michael Kirberger Xue Wang Hai Deng Wei Yang Guantao Chen Jenny J. Yang 《Journal of biological inorganic chemistry》2008,13(7):1169-1181
To better understand the biological significance of Ca2+, we report a comprehensive statistical analysis of calcium-binding proteins from the Protein Data Bank to identify structural parameters associated with EF-hand and non-EF-hand Ca2+-binding sites. Comparatively, non-EF-hand sites utilize lower coordination numbers (6 ± 2 vs. 7 ± 1), fewer protein ligands (4 ± 2 vs. 6 ± 1), and more water ligands (2 ± 2 vs. 1 ± 0) than EF-hand sites. The orders of ligand preference for non-EF-hand and EF-hand sites, respectively, were H2O (33.1%) > side-chain Asp (24.5%) > main-chain carbonyl (23.9%) > side-chain Glu (10.4%), and side-chain Asp (29.7%) > side-chain Glu (26.6%) > main-chain carbonyl (21.4%) > H2O (13.3%). Less formal negative charge was observed in the non-EF-hand than in the EF-hand binding sites (1 ± 1 vs. 3 ± 1). Additionally, over 20% of non-EF-hand sites had formal charge values of zero due to increased utilization of water and carbonyl oxygen ligands. Moreover, the EF-hand sites presented a narrower range of ligand distances and bond angles than non-EF-hand sites, possibly owing to the highly conserved helix–loop–helix motif. Significant differences between ligand types (carbonyl, side chain, bidentate) demonstrated that angles associated with each type must be classified separately, and the EF-hand side-chain Ca–O–C angles exhibited an unusual bimodal quality consistent with an Asp distribution that differed from the Gaussian model observed for non-EF-hand proteins. The results of this survey more accurately describe differences between EF-hand and non-EF-hand proteins and provide new parameters for the prediction and design of different classes of Ca2+-binding proteins. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Michael Kirberger, Xue Wang, and Hai Deng contributed equally to this article. 相似文献
17.
Plant calcium pumps, similarly to animal Ca2+ pumps, belong to the superfamily of P-type ATPase comprising also the plasma membrane H+-ATPase of fungi and plants, Na+/K+ ATPase of animals and H+/K+ ATPase of mammalian gastric mucosa. According to their sensitivity to calmodulin the plant Ca2+-ATPases have been divided into two subgroups: type IIA (homologues of animal SERCA) and type IIB (homologues of animal PMCA).
Regardless of the similarities in a protein sequence, the plant Ca2+ pumps differ from those in animals in their cellular localization, structure and sensitivity to inhibitors. Genomic investigations
revealed multiplicity of plant Ca2+-ATPases; they are present not only in the plasma membranes and ER but also in membranes of most of the cell compartments,
such as vacuole, plastids, nucleus or Golgi apparatus. Studies using yeast mutants made possible the functional and biochemical
characterization of individual plant Ca2+-ATMPases. Plant calcium pumps play an essential role in signal transduction pathways, they are responsible for the regulation
of [Ca2+] in both cytoplasm and endomembrane compartments. These Ca2+-ATPases appear to be involved in plant adaptation to stress conditions, like salinity, chilling or anoxia. 相似文献
18.
Zhainazarov AB 《The Journal of membrane biology》2003,193(2):91-98
A nonselective cation channel activated by intracellular Ca2+ was identified in inside-out membrane patches taken from cultured rat atrial myocytes. Ca2+ (0.01–1.00 mM) reversibly activated the channel in a concentration-dependent manner. The channel often showed a quick and irreversible rundown within a few minutes after patch excision. The I-V relationship of the channel was linear between –100 and +100 mV. The single channel conductance was 26.0 ± 0.5 pS and its open probability was weakly voltage-dependent. Ion-substitution experiments showed that the channel was permeable to monovalent cations (Px/PCs: Li+ (1.5) = K+ (1.5)> Na+ (1.2) > Rb+ (1.1) > Cs+ (1.0)) but not to Cl– (PCl/PCs < 0.01) and Ca2+ (PCa/PCs =0.02 ± 0.01).
Present address: A.B. Zhainazarov UF Center for Smell and Taste, McKnight Brain Institute, University of Florida, 100 S Newell Dr., L1-131, P.O. Box 100015, Gainesville, FL 32610-0015, USA 相似文献
19.
Xu L Chen J Li XY Ren S Huang CX Wu G Li XY Jiang XJ 《Molecular biology reports》2012,39(4):3847-3852
Na+/Ca2+ exchanger (NCX) plays important roles in cardiac electrical activity and calcium homeostasis. NCX current (INCX) shows transmural gradient across left ventricle in many species. Previous studies demonstrated that NCX expression was increased
and transmural gradient of INCX was disrupted in failing heart, but the mechanisms underlying INCX remodeling still remain unknown. In present study, we used patch clamp technique to record INCX from subepicardial (EPI) myocytes and subendocardial (ENDO) myocytes isolated from sham operation (SO) mice and heart failure
(HF) mice. Our results showed that INCX was higher in normal EPI cells compared with that in ENDO, whatever for forward mode or reverse mode. In HF group, INCX was significantly up-regulated, but EPI-ENDO difference was disrupted because of a more increase of INCX in ENDO myocytes. In order to explore the molecular mechanism underlying remodeling of INCX in failing heart, we detected the protein expression of NCX1 and Ca2+/calmodulin-dependent protein kinase II (CaMKII) by Western blot. We found that CaMKII activity was dramatically enhanced
and parallel with the expression of NCX1 in failing heart. Our study demonstrated that transmural gradient of INCX existed in murine left ventricle, and increased activity of CaMKII should account for INCX remodeling in failing heart. 相似文献
20.
The detailed mechanism of how lysophosphatidylcholine (LPC) suppresses endothelium-dependent vasodilatation is unclear at present. We investigated the effects of LPC on endothelial intracellular calcium (EC [Ca(2+)](i)) signaling and vascular tone simultaneously using a new technique we developed. Fura-2-labeled rat aortic specimens were mounted in a tissue flow chamber and precontracted with phenylephrine (5 x 10(-8) M). Under either basal or agonist-stimulated conditions, the EC [Ca(2+)](i) level was calculated from fura 2 fluorescence ratio images, and the vascular tone was estimated by measuring the relative displacement of the fluorescence images. Although both acetylcholine (ACh)-induced EC [Ca(2+)](i) elevation and the concomitant vasorelaxation were partially suppressed in specimens pretreated with LPC (20 microM), the quantitative relationship between EC [Ca(2+)](i) elevation and the corresponding vasorelaxation was unaffected. A high concentration of LPC (40 microM) completely eliminated ACh-evoked [Ca(2+)](i) elevation and vasodilatation. It has been reported that exposing vascular tissue to a calcium-free buffer causes a reduction in the EC [Ca(2+)](i) level and the accompanying vasoconstriction. Pretreatment with 20 microM LPC reduced the basal EC [Ca(2+)](i) level and abolished the calcium-free solution-induced EC [Ca(2+)](i) reduction and vasoconstriction. We conclude that LPC impairs endothelium-dependent vasorelaxation mainly by reducing the basal EC [Ca(2+)](i) level and suppressing agonist-evoked EC [Ca(2+)](i) signaling. 相似文献