共查询到20条相似文献,搜索用时 31 毫秒
1.
Isik Turker Chih-Chieh Yu Po-Cheng Chang Zhenhui Chen Yoshiro Sohma Shien-Fong Lin Peng-Sheng Chen Tomohiko Ai 《PloS one》2013,8(7)
Background
Apamin sensitive potassium current (I KAS), carried by the type 2 small conductance Ca2+-activated potassium (SK2) channels, plays an important role in post-shock action potential duration (APD) shortening and recurrent spontaneous ventricular fibrillation (VF) in failing ventricles.Objective
To test the hypothesis that amiodarone inhibits I KAS in human embryonic kidney 293 (HEK-293) cells.Methods
We used the patch-clamp technique to study I KAS in HEK-293 cells transiently expressing human SK2 before and after amiodarone administration.Results
Amiodarone inhibited IKAS in a dose-dependent manner (IC50, 2.67±0.25 µM with 1 µM intrapipette Ca2+). Maximal inhibition was observed with 50 µM amiodarone which inhibited 85.6±3.1% of IKAS induced with 1 µM intrapipette Ca2+ (n = 3). IKAS inhibition by amiodarone was not voltage-dependent, but was Ca2+-dependent: 30 µM amiodarone inhibited 81.5±1.9% of I KAS induced with 1 µM Ca2+ (n = 4), and 16.4±4.9% with 250 nM Ca2+ (n = 5). Desethylamiodarone, a major metabolite of amiodarone, also exerts voltage-independent but Ca2+ dependent inhibition of I KAS.Conclusion
Both amiodarone and desethylamiodarone inhibit I KAS at therapeutic concentrations. The inhibition is independent of time and voltage, but is dependent on the intracellular Ca2+ concentration. SK2 current inhibition may in part underlie amiodarone''s effects in preventing electrical storm in failing ventricles. 相似文献2.
Chunping Qian Jihua Ma Peihua Zhang Antao Luo Chao Wang Zhiqiang Ren Linghao Kong Shuo Zhang Xiaojing Wang Ying Wu 《PloS one》2012,7(12)
Background/Aims
Resveratrol has been demonstrated to be protective in the cardiovascular system. The aim of this study was to assess the effects of resveratrol on hydrogen peroxide (H2O2)-induced increase in late sodium current (I Na.L) which augmented the reverse Na+-Ca2+ exchanger current (I NCX), and the diastolic intracellular Ca2+ concentration in ventricular myocytes.Methods
I Na.L, I NCX, L-type Ca2+ current (I Ca.L) and intracellular Ca2+ properties were determined using whole-cell patch-clamp techniques and dual-excitation fluorescence photomultiplier system (IonOptix), respectively, in rabbit ventricular myocytes.Results
Resveratrol (10, 20, 40 and 80 µM) decreased I Na.L in myocytes both in the absence and presence of H2O2 (300 µM) in a concentration dependent manner. Ranolazine (3–9 µM) and tetrodotoxin (TTX, 4 µM), I Na.L inhibitors, decreased I Na.L in cardiomyocytes in the presence of 300 µM H2O2. H2O2 (300 µM) increased the reverse I NCX and this increase was significantly attenuated by either 20 µM resveratrol or 4 µM ranolazine or 4 µM TTX. In addition, 10 µM resveratrol and 2 µM TTX significantly depressed the increase by 150 µM H2O2 of the diastolic intracellular Ca2+ fura-2 fluorescence intensity (FFI), fura-fluorescence intensity change (△FFI), maximal velocity of intracellular Ca2+ transient rise and decay. As expected, 2 µM TTX had no effect on I Ca.L.Conclusion
Resveratrol protects the cardiomyocytes by inhibiting the H2O2-induced augmentation of I Na.L.and may contribute to the reduction of ischemia-induced lethal arrhythmias. 相似文献3.
Xiong W Liu T Wang Y Chen X Sun L Guo N Zheng H Zheng L Ruat M Han W Zhang CX Zhou Z 《PloS one》2011,6(10):e24573
Aim
Neurotransmitter release is elicited by an elevation of intracellular Ca2+ concentration ([Ca2+]i). The action potential triggers Ca2+ influx through Ca2+ channels which causes local changes of [Ca2+]i for vesicle release. However, any direct role of extracellular Ca2+ (besides Ca2+ influx) on Ca2+-dependent exocytosis remains elusive. Here we set out to investigate this possibility on rat dorsal root ganglion (DRG) neurons and chromaffin cells, widely used models for studying vesicle exocytosis.Results
Using photolysis of caged Ca2+ and caffeine-induced release of stored Ca2+, we found that extracellular Ca2+ inhibited exocytosis following moderate [Ca2+]i rises (2–3 µM). The IC50 for extracellular Ca2+ inhibition of exocytosis (ECIE) was 1.38 mM and a physiological reduction (∼30%) of extracellular Ca2+ concentration ([Ca2+]o) significantly increased the evoked exocytosis. At the single vesicle level, quantal size and release frequency were also altered by physiological [Ca2+]o. The calcimimetics Mg2+, Cd2+, G418, and neomycin all inhibited exocytosis. The extracellular Ca2+-sensing receptor (CaSR) was not involved because specific drugs and knockdown of CaSR in DRG neurons did not affect ECIE.Conclusion/Significance
As an extension of the classic Ca2+ hypothesis of synaptic release, physiological levels of extracellular Ca2+ play dual roles in evoked exocytosis by providing a source of Ca2+ influx, and by directly regulating quantal size and release probability in neuronal cells. 相似文献4.
Background
Hydrogen sulfide (H2S) functions as a neuromodulator, but whether it modulates visceral pain is not well known. This study was designed to determine the role for the endogenous H2S producing enzyme cystathionine β-synthetase (CBS) and cystathionine γ-lyase (CSE) in a validated rat model of visceral hyperalgesia (VH).Methods
VH was induced by nine-day heterotypic intermittent stress (HIS). Abdominal withdrawal reflex (AWR) scores were determined by measuring the visceromoter responses to colorectal distension (CRD). Dorsal root ganglia (DRG) neurons innervating the colon were labeled by injection of DiI (1,1''-dioleyl-3,3,3'',3-tetramethylindocarbocyanine methanesulfonate) into the colon wall. Patch clamp recording techniques were employed to examine excitability and sodium channel currents of colon specific DRG neurons. Tissues from colon related thoracolumbar DRGs were analyzed for CBS, CSE and sodium channel expression.Results
HIS significantly increased the visceromotor responses to CRD in association with an upregulated expression of CBS not CSE proteins in colon related DRGs. Administration of O-(Carboxymethyl)hydroxylamine hemihydrochloride (AOAA), an inhibitor of CBS, attenuated the AWR scores in HIS-treated rats, in a dose dependent fashion. In contrast, AOAA did not produce any effect on AWR scores in healthy control rats. AOAA reversed the potentiation of sodium channel current densities of colon specific DRG neurons of HIS rats. To further confirm the role for CBS-H2S signaling, NaHS was used to mimic the production of H2S by CBS. Application of NaHS significantly enhanced neuronal excitability and potentiated sodium channel current densities of colon DRG neurons from healthy control rats. Furthermore, AOAA reversed the upregulation of NaV1.7 and NaV1.8 in colon related DRGs of HIS rats.Conclusion
Our results suggest that upregulation of CBS expression might play an important role in developing VH via sensitization of sodium channels in peripheral nociceptors, thus identifying a specific neurobiological target for the treatment of VH in functional bowel syndromes. 相似文献5.
Virginie Prulière-Escabasse Christine Clerici Grégoire Vuagniaux Andre Coste Estelle Escudier Carole Planès 《Respiratory research》2010,11(1):141
Background
Hyperactivity of the epithelial sodium (Na+) channel (ENaC) and increased Na+ absorption by airway epithelial cells leading to airway surface liquid dehydration and impaired mucociliary clearance are thought to play an important role in the pathogenesis of cystic fibrosis (CF) pulmonary disease. In airway epithelial cells, ENaC is constitutively activated by endogenous trypsin-like serine proteases such as Channel-Activating Proteases (CAPs). It was recently reported that ENaC activity could also be stimulated by apical treatment with human neutrophil elastase (hNE) in a human airway epithelial cell line, suggesting that hNE inhibition could represent a novel therapeutic approach for CF lung disease. However, whether hNE can also activate Na+ reabsorption in primary human nasal epithelial cells (HNEC) from control or CF patients is currently unknown.Methods
We evaluated by short-circuit current (Isc) measurements the effects of hNE and EPI-hNE4, a specific hNE inhibitor, on ENaC activity in primary cultures of HNEC obtained from control (9) and CF (4) patients.Results
Neither hNE nor EPI-hNE4 treatments did modify Isc in control and CF HNEC. Incubation with aprotinin, a Kunitz-type serine protease inhibitor that blocks the activity of endogenous CAPs, decreased Isc by 27.6% and 54% in control and CF HNEC, respectively. In control and CF HNEC pretreated with aprotinin, hNE did significantly stimulate Isc, an effect which was blocked by EPI-hNE4.Conclusions
These results indicate that hNE does activate ENaC and transepithelial Na+ transport in both normal and CF HNEC, on condition that the activity of endogenous CAPs is first inhibited. The potent inhibitory effect of EPI-hNE4 on hNE-mediated ENaC activation observed in our experiments highlights that the use of EPI-hNE4 could be of interest to reduce ENaC hyperactivity in CF airways. 相似文献6.
Background
Although fibroblast-to-myocyte electrical coupling is experimentally suggested, electrophysiology of cardiac fibroblasts is not as well established as contractile cardiac myocytes. The present study was therefore designed to characterize ion channels in cultured human cardiac fibroblasts.Methods and Findings
A whole-cell patch voltage clamp technique and RT-PCR were employed to determine ion channels expression and their molecular identities. We found that multiple ion channels were heterogeneously expressed in human cardiac fibroblasts. These include a big conductance Ca2+-activated K+ current (BKCa) in most (88%) human cardiac fibroblasts, a delayed rectifier K+ current (IKDR) and a transient outward K+ current (Ito) in a small population (15 and 14%, respectively) of cells, an inwardly-rectifying K+ current (IKir) in 24% of cells, and a chloride current (ICl) in 7% of cells under isotonic conditions. In addition, two types of voltage-gated Na+ currents (INa) with distinct properties were present in most (61%) human cardiac fibroblasts. One was a slowly inactivated current with a persistent component, sensitive to tetrodotoxin (TTX) inhibition (INa.TTX, IC50 = 7.8 nM), the other was a rapidly inactivated current, relatively resistant to TTX (INa.TTXR, IC50 = 1.8 µM). RT-PCR revealed the molecular identities (mRNAs) of these ion channels in human cardiac fibroblasts, including KCa.1.1 (responsible for BKCa), Kv1.5, Kv1.6 (responsible for IKDR), Kv4.2, Kv4.3 (responsible for Ito), Kir2.1, Kir2.3 (for IKir), Clnc3 (for ICl), NaV1.2, NaV1.3, NaV1.6, NaV1.7 (for INa.TTX), and NaV1.5 (for INa.TTXR).Conclusions
These results provide the first information that multiple ion channels are present in cultured human cardiac fibroblasts, and suggest the potential contribution of these ion channels to fibroblast-myocytes electrical coupling. 相似文献7.
Patrick M. Boyle Carolyn J. Park Hermenegild J. Arevalo Edward J. Vigmond Natalia A. Trayanova 《PloS one》2014,9(1)
Background
Organ-scale arrhythmogenic consequences of source-sink mismatch caused by impaired excitability remain unknown, hindering the understanding of pathophysiology in disease states like Brugada syndrome and ischemia.Objective
We sought to determine whether sodium current (INa) reduction in the structurally normal heart unmasks a regionally heterogeneous substrate for the induction of sustained arrhythmia by premature ventricular contractions (PVCs).Methods
We conducted simulations in rabbit ventricular computer models with 930 unique combinations of PVC location (10 sites) and coupling interval (250–400 ms), INa reduction (30 or 40% of normal levels), and post-PVC sinus rhythm (arrested or persistent). Geometric characteristics and source-sink mismatch were quantitatively analyzed by calculating ventricular wall thickness and a newly formulated 3D safety factor (SF), respectively.Results
Reducing INa to 30% of its normal level created a substrate for sustained arrhythmia induction by establishing large regions of critical source-sink mismatch (SF<1) for ectopic wavefronts propagating from thin to thick tissue. In the same simulations but with 40% of normal INa, PVCs did not induce reentry because the volume of tissue with SF<1 was >95% smaller. Likewise, when post-PVC sinus activations were persistent instead of arrested, no ectopic excitations initiated sustained reentry because sinus activation breakthroughs engulfed the excitable gap.Conclusion
Our new SF formulation can quantify ectopic wavefront propagation robustness in geometrically complex 3D tissue with impaired excitability. This novel methodology was applied to show that INa reduction precipitates source-sink mismatch, creating a potent substrate for sustained arrhythmia induction by PVCs originating near regions of ventricular wall expansion, such as the RV outflow tract. 相似文献8.
Background
DrTx(1-42) (a carboxyl-terminally truncated version of drosotoxin) is a potent and selective blocker of tetrodotoxin-resistant (TTX-R) Na+ channels in rat dorsal root ganglion neurons with analgesic activity. This purpose is to identify key amino acids which are responsible for both blocking and analgesic effects of DrTx(1-42).Methods
On the basis of previous study, we designed five mutants of DrTx(1-42) (delN, D8A, D8K, G9A, and G9R) in the amino-terminal turn (N-turn) region, a proposed functional region located in the amino-terminus of the molecule. All these mutants were expressed in E.coli and purified by RP-HPLC. Electrophysiological properties of these analogues were examined by whole-cell patch-clamp recordings and their antinociceptive effects were investigated by the formalin test and acetic acid induced writhing test.Results
All the mutants except for G9A possess a similar secondary structure to that of DrTx(1-42), as identified by circular dichroism analysis. Three mutants (delN, D8A and G9A) were found almost inactive to TTX-R Na+ channels, whereas D8K retains similar activity and G9R showed decreased potency when compared with the wild-type molecule. Consistent with the electrophysiological observations, D8K and G9R exhibited antinociceptive effects in the second phase (inflammatory pain) of the formalin test and the acetic acid induced writhing test, while delN, D8A and G9A lack such effects.Conclusions
Our results show that the N-turn is closely related to function of DrTx(1-42). The mutant (D8A) as a control peptide further reveals that a charged residue at site 8 of the N-terminus is important for channel blockade and analgesic activity. This study indicates that blocking of voltage-gated TTX-R Na+ channel in DRG neurons contributes to analgesic effect in rat inflammatory pain. Structural and functional data described here offers support for the development of novel analgesic drugs through targeting TTX-R Na+ channels. 相似文献9.
Michael Schemann Eva Maria Kugler Sabine Buhner Christopher Eastwood Jemma Donovan Wen Jiang David Grundy 《PloS one》2012,7(12)
Background
Compound 48/80 is widely used in animal and tissue models as a “selective” mast cell activator. With this study we demonstrate that compound 48/80 also directly activates enteric neurons and visceral afferents.Methodology/Principal Findings
We used in vivo recordings from extrinsic intestinal afferents together with Ca++ imaging from primary cultures of DRG and nodose neurons. Enteric neuronal activation was examined by Ca++ and voltage sensitive dye imaging in isolated gut preparations and primary cultures of enteric neurons. Intraluminal application of compound 48/80 evoked marked afferent firing which desensitized on subsequent administration. In egg albumen-sensitized animals, intraluminal antigen evoked a similar pattern of afferent activation which also desensitized on subsequent exposure to antigen. In cross-desensitization experiments prior administration of compound 48/80 failed to influence the mast cell mediated response. Application of 1 and 10 µg/ml compound 48/80 evoked spike discharge and Ca++ transients in enteric neurons. The same nerve activating effect was observed in primary cultures of DRG and nodose ganglion cells. Enteric neuron cultures were devoid of mast cells confirmed by negative staining for c-kit or toluidine blue. In addition, in cultured enteric neurons the excitatory action of compound 48/80 was preserved in the presence of histamine H1 and H2 antagonists. The mast cell stabilizer cromolyn attenuated compound 48/80 and nicotine evoked Ca++ transients in mast cell-free enteric neuron cultures.Conclusions/Significance
The results showed direct excitatory action of compound 48/80 on enteric neurons and visceral afferents. Therefore, functional changes measured in tissue or animal models may involve a mast cell independent effect of compound 48/80 and cromolyn. 相似文献10.
Background
Apamin is commonly used as a small-conductance Ca2+-activated K+ (SK) current inhibitor. However, the specificity of apamin in cardiac tissues remains unclear.Objective
To test the hypothesis that apamin does not inhibit any major cardiac ion currents.Methods
We studied human embryonic kidney (HEK) 293 cells that expressed human voltage-gated Na+, K+ and Ca2+ currents and isolated rabbit ventricular myocytes. Whole-cell patch clamp techniques were used to determine ionic current densities before and after apamin administration.Results
Ca2+ currents (CACNA1c+CACNB2b) were not affected by apamin (500 nM) (data are presented as median [25th percentile;75th percentile] (from –16 [–20;–10] to –17 [–19;–13] pA/pF, P = NS), but were reduced by nifedipine to –1.6 [–3.2;–1.3] pA/pF (p = 0.008). Na+ currents (SCN5A) were not affected by apamin (from –261 [–282;–145] to –268 [–379;–132] pA/pF, P = NS), but were reduced by flecainide to –57 [–70;–47] pA/pF (p = 0.018). None of the major K+ currents (I Ks, I Kr, I K1 and I to) were inhibited by 500 nM of apamin (KCNQ1+KCNE1, from 28 [20]; [37] to 23 [18]; [32] pA/pF; KCNH2+KCNE2, from 28 [24]; [30] to 27 [24]; [29] pA/pF; KCNJ2, from –46 [–48;–40] to –46 [–51;–35] pA/pF; KCND3, from 608 [505;748] to 606 [454;684]). Apamin did not inhibit the I Na or I CaL in isolated rabbit ventricular myocytes (I Na, from –67 [–75;–59] to –68 [–71;–59] pA/pF; I CaL, from –16 [–17;–14] to –14 [–15;–13] pA/pF, P = NS for both).Conclusions
Apamin does not inhibit human cardiac Na+ currents, L-type Ca2+ currents or other major K+ currents. These findings indicate that apamin is a specific SK current inhibitor in hearts as well as in other organs. 相似文献11.
Heming Wei Guangqin Zhang Suhua Qiu Jun Lu Jingwei Sheng Manasi Grace Tan Philip Wong Shu Uin Gan Winston Shim 《PloS one》2012,7(11)
Aim
Hydrogen sulfide (H2S) is a promising cardioprotective agent and a potential modulator of cardiac ion currents. Yet its cardiac effects on humans are poorly understood due to lack of functional cardiomyocytes. This study investigates electrophysiological responses of human pluripotent stem cells (hPSCs) derived cardiomyocytes towards H2S.Methods and Results
Cardiomyocytes of ventricular, atrial and nodal subtypes differentiated from H9 embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) were electrophysiologically characterized. The effect of NaHS, a donor of H2S, on action potential (AP), outward rectifier potassium currents (I Ks and I Kr), L-type Ca2+ currents (I CaL) and hyperpolarization-activated inward current (I f) were determined by patch-clamp electrophysiology and confocal calcium imaging. In a concentration-dependent manner, NaHS (100 to 300 µM) consistently altered the action potential properties including prolonging action potential duration (APD) and slowing down contracting rates of ventricular-and atrial-like cardiomyocytes derived from both hESCs and hiPSCs. Moreover, inhibitions of slow and rapid I K (I Ks and I Kr), I CaL and I f were found in NaHS treated cardiomyocytes and it could collectively contribute to the remodeling of AP properties.Conclusions
This is the first demonstration of effects of H2S on cardiac electrophysiology of human ventricular-like, atrial-like and nodal-like cardiomyocytes. It reaffirmed the inhibitory effect of H2S on I CaL and revealed additional novel inhibitory effects on I f, I Ks and I Kr currents in human cardiomyocytes. 相似文献12.
13.
Background and Purpose
The root extract of the African Uzara plant is used in traditional medicine as anti-diarrheal drug. It is known to act via inhibition of intestinal motility, but malabsorptive or antisecretory mechanisms are unknown yet.Experimental Approach
HT-29/B6 cells and human colonic biopsies were studied in Ussing experiments in vitro. Uzara was tested on basal as well as on forskolin- or cholera toxin-induced Cl− secretion by measuring short-circuit current (ISC) and tracer fluxes of 22Na+ and 36Cl−. Para- and transcellular resistances were determined by two-path impedance spectroscopy. Enzymatic activity of the Na+/K+-ATPase and intracellular cAMP levels (ELISA) were measured.Key Results
In HT-29/B6 cells, Uzara inhibited forskolin- as well as cholera toxin-induced ISC within 60 minutes indicating reduced active chloride secretion. Similar results were obtained in human colonic biopsies pre-stimulated with forskolin. In HT-29/B6, the effect of Uzara on the forskolin-induced ISC was time- and dose-dependent. Analyses of the cellular mechanisms of this Uzara effect revealed inhibition of the Na+/K+-ATPase, a decrease in forskolin-induced cAMP production and a decrease in paracellular resistance. Tracer flux experiments indicate that the dominant effect is the inhibition of the Na+/K+-ATPase.Conclusion and Implications
Uzara exerts anti-diarrheal effects via inhibition of active chloride secretion. This inhibition is mainly due to an inhibition of the Na+/K+-ATPase and to a lesser extent to a decrease in intracellular cAMP responses and paracellular resistance. The results imply that Uzara is suitable for treating acute secretory diarrhea. 相似文献14.
15.
16.
Attila Kristóf Zoltán Husti István Koncz Zsófia Kohajda Tamás Szél Viktor Juhász Péter Biliczki Norbert Jost István Baczkó Julius Gy Papp András Varró László Virág 《PloS one》2012,7(12)
Background
The aim of the present work was to characterize the electrophysiological effects of the non-steroidal anti-inflammatory drug diclofenac and to study the possible proarrhythmic potency of the drug in ventricular muscle.Methods
Ion currents were recorded using voltage clamp technique in canine single ventricular cells and action potentials were obtained from canine ventricular preparations using microelectrodes. The proarrhythmic potency of the drug was investigated in an anaesthetized rabbit proarrhythmia model.Results
Action potentials were slightly lengthened in ventricular muscle but were shortened in Purkinje fibers by diclofenac (20 µM). The maximum upstroke velocity was decreased in both preparations. Larger repolarization prolongation was observed when repolarization reserve was impaired by previous BaCl2 application. Diclofenac (3 mg/kg) did not prolong while dofetilide (25 µg/kg) significantly lengthened the QTc interval in anaesthetized rabbits. The addition of diclofenac following reduction of repolarization reserve by dofetilide further prolonged QTc. Diclofenac alone did not induce Torsades de Pointes ventricular tachycardia (TdP) while TdP incidence following dofetilide was 20%. However, the combination of diclofenac and dofetilide significantly increased TdP incidence (62%). In single ventricular cells diclofenac (30 µM) decreased the amplitude of rapid (IKr) and slow (IKs) delayed rectifier currents thereby attenuating repolarization reserve. L-type calcium current (ICa) was slightly diminished, but the transient outward (Ito) and inward rectifier (IK1) potassium currents were not influenced.Conclusions
Diclofenac at therapeutic concentrations and even at high dose does not prolong repolarization markedly and does not increase the risk of arrhythmia in normal heart. However, high dose diclofenac treatment may lengthen repolarization and enhance proarrhythmic risk in hearts with reduced repolarization reserve. 相似文献17.
Yu-Li Luo Hong-Mei Guo Yi-Lin Zhang Peng-Xiao Chen Yun-Xin Zhu Jie-Hong Huang Wen-Liang Zhou 《PloS one》2013,8(1)
Background
Recent studies suggest that formaldehyde (FA) could be synthesized endogeneously and transient receptor potential (TRP) channel might be the sensor of FA. However, the physiological significance is still unclear.Methodology/Principal Findings
The present study investigated the FA induced epithelial Cl- secretion by activation of TRPV-1 channel located in the nerve ending fiber. Exogenously applied FA induced an increase of I SC in intact rat trachea tissue but not in the primary cultured epithelial cells. Western blot and immunofluorescence analysis identified TRPV-1 expression in rat tracheal nerve ending. Capsazepine (CAZ), a TRPV-1 specific antagonist significantly blocked the I SC induced by FA. The TRPV-1 agonist capsaicin (Cap) induced an increase of I SC, which was similar to the I SC induced by FA. L-703606, an NK-1 specific inhibitor and propranolol, an adrenalin β receptor inhibitor significantly abolished the I SC induced by FA or Cap. In the ion substitute analysis, FA could not induce I SC in the absence of extracelluar Cl-. The I SC induced by FA could be blocked by the non-specific Cl- channel inhibitor DPC and the CFTR specific inhibitor CFTRi-172, but not by the Ca2+-activated Cl- channel inhibitor DIDS. Furthermore, both forskolin, an agonist of adenylate cyclase (AC) and MDL-12330A, an antagonist of AC could block FA-induced I SC.Conclusion
Our results suggest that FA-induced epithelial I SC response is mediated by nerve, involving the activation of TRPV-1 and release of adrenalin as well as substance P. 相似文献18.
Background
The SCN5A encoded sodium current (INa) generates the action potential (AP) upstroke and is a major determinant of AP characteristics and AP propagation in cardiac myocytes. Unfortunately, in cardiac myocytes, investigation of kinetic properties of INa with near-physiological ion concentrations and temperature is technically challenging due to the large amplitude and rapidly activating nature of INa, which may seriously hamper the quality of voltage control over the membrane. We hypothesized that the alternating voltage clamp-current clamp (VC/CC) technique might provide an alternative to traditional voltage clamp (VC) technique for the determination of INa properties under physiological conditions.Principal Findings
We studied INa under close-to-physiological conditions by VC technique in SCN5A cDNA-transfected HEK cells or by alternating VC/CC technique in both SCN5A cDNA-transfected HEK cells and rabbit left ventricular myocytes. In these experiments, peak INa during a depolarizing VC step or maximal upstroke velocity, dV/dtmax, during VC/CC served as an indicator of available INa. In HEK cells, biophysical properties of INa, including current density, voltage dependent (in)activation, development of inactivation, and recovery from inactivation, were highly similar in VC and VC/CC experiments. As an application of the VC/CC technique we studied INa in left ventricular myocytes isolated from control or failing rabbit hearts.Conclusions
Our results demonstrate that the alternating VC/CC technique is a valuable experimental tool for INa measurements under close-to-physiological conditions in cardiac myocytes. 相似文献19.
Background
The rate-limiting step that determines the dominant time constant (τD) of mammalian rod photoresponse recovery is the deactivation of the active phosphodiesterase (PDE6). Physiologically relevant Ca2+-dependent mechanisms that would affect the PDE inactivation have not been identified. However, recently it has been shown that τD is modulated by background light in mouse rods.Methodology/Principal Findings
We used ex vivo ERG technique to record pharmacologically isolated photoreceptor responses (fast PIII component). We show a novel static effect of calcium on mouse rod phototransduction: Ca2+ shortens the dominant time constant (τD) of saturated photoresponse recovery, i.e., when extracellular free Ca2+ is decreased from 1 mM to ∼25 nM, the τD is reversibly increased ∼1.5–2-fold.Conclusions
We conclude that the increase in τD during low Ca2+ treatment is not due to increased [cGMP], increased [Na+] or decreased [ATP] in rod outer segment (ROS). Also it cannot be due to protein translocation mechanisms. We suggest that a Ca2+-dependent mechanism controls the life time of active PDE. 相似文献20.
Targeted Deletion of Kcne2 Impairs HCN Channel Function in Mouse Thalamocortical Circuits 总被引:1,自引:0,他引:1