scholarly journals Methylene blue counteracts cyanide cardiotoxicity: cellular mechanisms

2018 ◽  
Vol 124 (5) ◽  
pp. 1164-1176 ◽  
Author(s):  
Joseph Y. Cheung ◽  
JuFang Wang ◽  
Xue-Qian Zhang ◽  
Jianliang Song ◽  
Dhanendra Tomar ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Membrane Potential ◽  
Adenosine Triphosphate ◽  
Early Stage ◽  
Left Ventricular ◽  
Smoke Inhalation ◽  
Resting Membrane Potential ◽  
Cellular Mechanisms ◽  
Oxidation Reduction ◽  
Intracellular Ca

In adult left ventricular mouse myocytes, exposure to sodium cyanide (NaCN) in the presence of glucose dose-dependently reduced contraction amplitude, with ~80% of maximal inhibitory effect attained at 100 µM. NaCN (100 µM) exposure for 10 min significantly decreased contraction and intracellular Ca2+ concentration ([Ca2+]i) transient amplitudes, systolic but not diastolic [Ca2+]i, and maximal L-type Ca2+ current ( ICa) amplitude, indicating acute alteration of [Ca2+]i homeostasis largely accounted for the observed excitation-contraction abnormalities. In addition, NaCN depolarized resting membrane potential ( Em), reduced action potential (AP) amplitude, prolonged AP duration at 50% (APD50) and 90% repolarization (APD90), and suppressed depolarization-activated K+ currents but had no effect on Na+-Ca2+ exchange current ( INaCa). NaCN did not affect cellular adenosine triphosphate levels but depolarized mitochondrial membrane potential (ΔΨm) and increased superoxide (O2·−) levels. Methylene blue (MB; 20 µg/ml) added 3 min after NaCN restored contraction and [Ca2+]i transient amplitudes, systolic [Ca2+]i, Em, AP amplitude, APD50, APD90, ICa, depolarization-activated K+ currents, ΔΨm, and O2·− levels toward normal. We conclude that MB reversed NaCN-induced cardiotoxicity by preserving intracellular Ca2+ homeostasis and excitation-contraction coupling ( ICa), minimizing risks of arrhythmias ( Em, AP configuration, and depolarization-activated K+ currents), and reducing O2·− levels. NEW & NOTEWORTHY Cyanide poisoning due to industrial exposure, smoke inhalation, and bioterrorism manifests as cardiogenic shock and requires rapidly effective antidote. In the early stage of cyanide exposure, adenosine triphosphate levels are normal but myocyte contractility is reduced, largely due to alterations in Ca2+ homeostasis because of changes in oxidation-reduction environment of ion channels. Methylene blue, a drug approved by the U.S. Food and Drug Administration, ameliorates cyanide toxicity by normalizing oxidation-reduction state and Ca2+ channel function.

Influence of age and run training on cardiac Na+/Ca2+ exchange

2003 ◽  
Vol 95 (5) ◽  
pp. 1994-2003 ◽  
Author(s):  
Lisa C. Mace ◽  
Bradley M. Palmer ◽  
David A. Brown ◽  
Korinne N. Jew ◽  
Joshua M. Lynch ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Left Ventricular ◽  
Brown Norway ◽  
Resting Membrane Potential ◽  
Whole Cell Patch Clamp ◽  
Age Related ◽  
Intracellular Ca ◽  
Whole Heart ◽  
Exchange Activity

Effects of age and training on myocardial Na+/Ca2+ exchange were examined in young sedentary (YS; 14-15 mo), aged sedentary (AS; 27-31 mo), and aged trained (AT; 8- to 11-wk treadmill run training) male Fischer Brown Norway rats. Whole heart performance and isolated cardiocyte Na+/Ca2+ exchange characteristics were measured. At the whole heart level, a small but significant slowing of late isovolumic left ventricular (LV) relaxation, which may be indicative of altered Na+/Ca2+ exchange activity, was seen in hearts from AS rats. This subtle impairment in relaxation was not observed in hearts from AT rats. At the single-cardiocyte level, late action potential duration was prolonged, resting membrane potential was more positive, and overshoot potential was greater in cardiocytes from AS rats than from YS rats ( P < 0.05). Training did not influence any of these age-related action potential characteristics. In electrically paced cardiocytes, neither shortening nor intracellular Ca2+ concentration ([Ca2+]i) dynamics was influenced by age or training. Similarly, neither age nor training influenced the rate of [Ca2+]i clearance via forward (Nain+ /Caout2+) Na+/Ca2+ exchange after caffeine-induced Ca2+ release from the sarcoplasmic reticulum or cardiac Na+/Ca2+ exchanger protein (NCX1) expression. However, when whole cell patch-clamp techniques combined with fluorescence microscopy were used to evaluate the ability of Na+/Ca2+ exchange to alter cytosolic [Ca2+] ([Ca2+]c) under conditions where membrane potential ( Vm) and internal and external [Na+] and [Ca2+] could be controlled, we observed age-associated increases in forward Na+/Ca2+ exchange-mediated [Ca2+]c clearance ( P < 0.05) that were not influenced by training. The age-related increase in forward Na+/Ca2+ exchange activity provides a hypothetical explanation for the late action potential prolongation observed in this study.

Nonspiking interneurons in walking system of the cockroach

1975 ◽  
Vol 38 (1) ◽  
pp. 33-52 ◽  
Author(s):  
K. G. Pearson ◽  
C. R. Fourtner
Keyword(s):  
Membrane Potential ◽  
Periplaneta Americana ◽  
Rhythmic Activity ◽  
Synaptic Activity ◽  
Cobalt Sulfide ◽  
Resting Membrane Potential ◽  
Cellular Mechanisms ◽  
Metathoracic Ganglion ◽  
Nonspiking Interneurons ◽  
Leg Movements

Intracellular recordings were made from the neurites of interneurons and motoneurons in the metathoracic ganglion of the cockroach, Periplaneta americana. Many neurons were penetrated which failed to produce action potentials on the application of large depolarizing currents. Nevertheless, some of them strongly excited and/or inhibited slow motoneurons innervating leg musculature, even with weak depolariziing musculature, even with weak depolarizing currents. Cobalt-sulfide-straining of these nonspiking neurons showed them to be interneurons with their neurites contained entirely within the metathoracic ganglion. Two further characteristics of these interneurons were rapid spontaneous fluctuations in membrane potential and a low resting membrane potential. One nonspiking neuron, interneuron I, when depolarized caused a strong excitation of the set of slow levator motoneurons which discharge in bursts during stepping movements of the metathoracic leg. During rhythmic leg movements the membrane potential of interneuron I oscillated with the depolarizing phases occurring at the same time as bursts of activity in the levator motorneurons. No spiking or any other nonspiking neuron was penetrated which could excite these levator motoneurons. From all these observations we conclude that oscillations in the membrane potential of interneuron I are entirely responsible for producing the levator bursts, and thus for producing stepping movements in a walking animal. During rhythmic leg movements, bursts of activity in levator and depressor motoneurons are initiated by slow graded depolarizations. The similarity of the synaptic activity in these two types of motoneurons suggests that burst activity in the depressor motoneurons is also produced by rhythmic activity in nonspiking interneurons. The fact that no spiking neuron was found to excite the depressor motoneurons supports this conclusion. Interneuron I is also an element of the rhythm-generating system, since short depolarizing pulses applied to it during rhythmic activity could reset the thythm. Long-duration current pulses applied to interneuron I in a quiescent animal did not produce rhythmic activity. This observation, together with the finding that during rhythmic activity the slow depolarizations in interneuron I are usually terminated by IPSPs, suggests that interneuron I alone does not generate the rhythm. No spiking interneurons have yet been enccountered which influence the activity in levator motoneurons. Thus, we conclude that the rhythm is generated in a network of nonspiking interneurons. The cellular mechanisms for generating the oscillations in this network are unknown. Continued.

Propofol and thiopental attenuate adenosine triphosphate-sensitive potassium channel relaxation in pulmonary veins

2006 ◽  
Vol 291 (4) ◽  
pp. L636-L643 ◽  
Author(s):  
Woon-Seok Roh ◽  
Xueqin Ding ◽  
Paul A. Murray
Keyword(s):  
Nitric Oxide ◽  
Adenosine Triphosphate ◽  
Pulmonary Veins ◽  
Inhibitory Effect ◽  
Cellular Mechanisms ◽  
Voltage Gated ◽  
Channel Inhibition ◽  
Dependent Component ◽  
Intracellular Ca ◽  
Oxide Synthase

Pulmonary veins (PV) make a significant contribution to total pulmonary vascular resistance. We investigated the cellular mechanisms by which the intravenous anesthetics propofol and thiopental alter adenosine triphosphate-sensitive potassium (KATP+) channel relaxation in canine PV. The effects of KATP+ channel inhibition (glybenclamide), cyclooxygenase inhibition (indomethacin), nitric oxide synthase inhibition (l-NAME), and L-type voltage-gated Ca2+ channel inhibition (nifedipine) on vasorelaxation responses to levcromakalim (KATP+ channel activator) alone and in combination with the anesthetics were assessed. The maximal relaxation response to levcromakalim was attenuated by removing the endothelium and by l-NAME, but not by indomethacin. Propofol (10−5, 3 × 10−5, and 10−4 M) and thiopental (10−4 and 3 × 10−4 M) each attenuated levcromakalim relaxation in endothelium-intact (E+) rings, whereas propofol (3 × 10−5 and 10−4 M) and thiopental (3 × 10−4 M) attenuated levcromakalim relaxation in endothelium-denuded (E−) rings. In E+ rings, the anesthesia-induced attenuation of levcromakalim relaxation was decreased after pretreatment with l-NAME but not with indomethacin. In E-strips, propofol (10−4 M) and thiopental (3 × 10−4 M) inhibited decreases in tension and intracellular Ca2+ concentration ([Ca2+]i) in response to levcromakalim, and these changes were abolished by nifedipine. These findings indicate that propofol and thiopental attenuate the endothelium-dependent component of KATP+ channel-induced PV vasorelaxation via an inhibitory effect on the nitric oxide pathway. Both anesthetics also attenuate the PV smooth muscle component of KATP+ channel-induced relaxation by reducing the levcromakalim-induced decrease in [Ca2+]i via an inhibitory effect on L-type voltage-gated Ca2+ channels.

Endurance training alters outward K+current characteristics in rat cardiocytes

2001 ◽  
Vol 90 (4) ◽  
pp. 1327-1333 ◽  
Author(s):  
Korinne N. Jew ◽  
M. Charlotte Olsson ◽  
Eric A. Mokelke ◽  
Bradley M. Palmer ◽  
Russell L. Moore
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Primary Culture ◽  
Left Ventricular ◽  
Resting Membrane Potential ◽  
Sprague Dawley ◽  
Whole Cell ◽  
Time To Peak ◽  
Time Required ◽  
In Cells

The effect of endurance run training on outward K+ currents with rapidly inactivating ( I to) and sustained or slowly inactivating ( I sus) characteristics was examined in left ventricular (LV) cardiocytes isolated from sedentary (Sed) and treadmill-trained (Tr) female Sprague-Dawley rats. Isolated LV cardiocytes were used in whole cell patch-clamp studies to characterize whole cell I to and I sus. Peak I to was greatest in cells isolated from the Tr group. When I to was corrected for cell capacitance to yield a current density, most, but not all, of the Sed vs. Tr differences in I to magnitude were eliminated. Regardless of how I to was expressed (e.g., I to or I todensity), the time required to achieve a peak value was markedly shortened in the cardiocytes isolated from the Tr group. Training elicited a reduction in I sus density. Action potential characteristics were determined in Sed and Tr cardiocytes in primary culture. Training did not affect resting membrane potential, whereas peak membrane potential was reduced and time to peak membrane potential was prolonged in the Tr group. In addition, time to 50% repolarization was significantly increased in cells from the Tr group. Collectively, these data indicate that I to and I sus characteristics are altered by training in isolated LV cardiocytes. These alterations in I to and I sus may be responsible, at least in part, for the training-induced alterations in action potential configuration in cardiocytes in primary culture.

scholarly journals Mechanistic Role of I f Revealed by Induction of Ventricular Automaticity by Somatic Gene Transfer of Gating-Engineered Pacemaker (HCN) Channels

Circulation ◽  
2007 ◽  
Vol 115 (14) ◽  
pp. 1839-1850 ◽  
Author(s):  
Tian Xue ◽  
Chung-Wah Siu ◽  
Deborah K. Lieu ◽  
Chu-Pak Lau ◽  
Hung-Fat Tse ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Ectopic Expression ◽  
Left Ventricular ◽  
Intermediate Phenotype ◽  
Resting Membrane Potential ◽  
Hcn Channels ◽  
Adrenergic Stimulation ◽  
Biophysical Parameters ◽  
Direct Role

Background— Although I f , encoded by the hyperpolarization-activated cyclic-nucleotide-modulated (HCN) channel gene family, is known to be functionally important in pacing, its mechanistic action is largely inferential and indeed somewhat controversial. To dissect in detail the role of I f , we investigated the functional consequences of overexpressing in adult guinea pig left ventricular cardiomyocytes (LVCMs) various HCN1 constructs that have been engineered to exhibit different gating properties. Methods and Results— We created the recombinant adenoviruses Ad-CMV-GFP-IRES (CGI), Ad-CGI-HCN1, Ad-CGI-HCN1-ΔΔΔ, and Ad-CGI-HCN1-Ins, which mediate ectopic expression of GFP alone, WT, EVY235-7ΔΔΔ, and Ins HCN1 channels, respectively; EVY235-7ΔΔΔ and Ins encode channels in which the S3–S4 linkers have been shortened and lengthened to favor and inhibit opening, respectively. Ad-CGI-HCN1, Ad-CGI-HCN1-ΔΔΔ, and Ad-CGI-HCN1-Ins, but not control Ad-CGI, transduction of LVCMs led to robust expression of I f with comparable densities when fully open (≈−22 pA/pF at −140 mV; P >0.05) but distinctive activation profiles (V 1/2 =−70.8±0.6, −60.4±0.7, and −87.7±0.7 mV; P <0.01, respectively). Whereas control (nontransduced or Ad-CGI–transduced) LVCMs were electrically quiescent, automaticity (206±16 bpm) was observed exclusively in 61% of Ad-HCN1-ΔΔΔ–transduced cells that displayed depolarized maximum diastolic potential (−60.6±0.5 versus −70.6±0.6 mV of resting membrane potential of control cells; P <0.01) and gradual phase 4 depolarization (306±32 mV/s) that were typical of genuine nodal cells. Furthermore, spontaneously firing Ad-HCN1-ΔΔΔ–transduced LVCMs responded positively to adrenergic stimulation ( P <0.05) but exhibited neither overdrive excitation nor suppression. In contrast, the remaining 39% of Ad-HCN1-ΔΔΔ–transduced cells exhibited no spontaneous action potentials; however, a single ventricular action potential associated with a depolarized resting membrane potential and a unique, incomplete “phase 4–like” depolarization that did not lead to subsequent firing could be elicited on simulation. Such an intermediate phenotype, similarly observed in 100% of Ad-CGI-HCN– and Ad-CGI-HCN1-Ins–transduced LVCMs, could be readily reversed by ZD7288, hinting at a direct role of I f . Correlation analysis revealed the specific biophysical parameters required for I f to function as an active membrane potential oscillator. Conclusions— Our results not only contribute to a better understanding of cardiac pacing but also may advance current efforts that focus primarily on automaticity induction to the next level by enabling bioengineering of central and peripheral cells that make up the native sinoatrial node.

Effects of Na+/Ca2+ exchanger downregulation on contractility and [Ca2+]i transients in adult rat myocytes

2002 ◽  
Vol 283 (4) ◽  
pp. H1616-H1626 ◽  
Author(s):  
George M. Tadros ◽  
Xue-Qian Zhang ◽  
Jianliang Song ◽  
Lois L. Carl ◽  
Lawrence I. Rothblum ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Sarcoplasmic Reticulum ◽  
Current Density ◽  
Resting Membrane Potential ◽  
Action Potential Amplitude ◽  
Half Time ◽  
Adult Rat ◽  
Postmyocardial Infarction ◽  
Intracellular Ca ◽  
Rat Myocytes

Postmyocardial infarction (MI) rat myocytes demonstrated depressed Na+/Ca2+exchange (NCX1) activity, altered contractility, and intracellular Ca2+ concentration ([Ca2+]i) transients. We investigated whether NCX1 downregulation in normal myocytes resulted in contractility changes observed in MI myocytes. Myocytes infected with adenovirus expressing antisense (AS) oligonucleotides to NCX1 had 30% less NCX1 at 3 days and 66% less NCX1 at 6 days. The half-time of relaxation from caffeine-induced contracture was twice as long in ASNCX1 myocytes. Sarcoplasmic reticulum (SR) Ca2+-ATPase abundance, SR Ca2+uptake, resting membrane potential, action potential amplitude and duration, L-type Ca2+ current density and cell size were not affected by ASNCX1 treatment. At extracellular Ca2+ concentration ([Ca2+]o) of 5 mM, ASNCX1 myocytes had significantly lower contraction and [Ca2+]i transient amplitudes and SR Ca2+ contents than control myocytes. At 0.6 mM [Ca2+]o, contraction and [Ca2+]i transient amplitudes and SR Ca2+ contents were significantly higher in ASNCX1 myocytes. At 1.8 mM [Ca2+]o, contraction and [Ca2+]i transient amplitudes were not different between control and ASNCX1 myocytes. This pattern of contractile and [Ca2+]i transient abnormalities in ASNCX1 myocytes mimics that observed in rat MI myocytes. We conclude that downregulation of NCX1 in adult rat myocytes resulted in decreases in both Ca2+ influx and efflux during a twitch. We suggest that depressed NCX1 activity may partly account for the contractile abnormalities after MI.

48-h Hypoxic exposure results in endothelium-dependent systemic vascular smooth muscle cell hyperpolarization

2002 ◽  
Vol 283 (1) ◽  
pp. R79-R85 ◽  
Author(s):  
Scott Earley ◽  
Jay S. Naik ◽  
Benjimen R. Walker
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Vascular Smooth Muscle ◽  
Vessel Wall ◽  
Hypoxic Exposure ◽  
Resting Membrane Potential ◽  
Resistance Arteries ◽  
Adrenergic Agonist ◽  
Intracellular Ca ◽  
Oxide Synthase

Chronic hypoxia (CH) results in reduced sensitivity to vasoconstrictors in conscious rats that persists upon restoration of normoxia. We hypothesized that this effect is due to endothelium-dependent hyperpolarization of vascular smooth muscle (VSM) cells after CH. VSM cell resting membrane potential was determined for superior mesenteric artery strips isolated from CH rats (Pb = 380 Torr for 48 h) and normoxic controls. VSM cells from CH rats studied under normoxia were hyperpolarized compared with controls. Resting vessel wall intracellular Ca2+ concentration ([Ca2+]i) and pressure-induced vasoconstriction were reduced in vessels isolated from CH rats compared with controls. Vasoconstriction and increases in vessel wall [Ca2+]i in response to the α1-adrenergic agonist phenylephrine (PE) were also blunted in resistance arteries from CH rats. Removal of the endothelium normalized resting membrane potential, resting vessel wall [Ca2+]i, pressure-induced vasoconstrictor responses, and PE-induced constrictor and Ca2+ responses between groups. Whereas VSM cell hyperpolarization persisted in the presence of nitric oxide synthase inhibition, heme oxygenase inhibition restored VSM cell resting membrane potential in vessels from CH rats to control levels. We conclude that endothelial derived CO accounts for persistent VSM cell hyperpolarization and vasoconstrictor hyporeactivity after CH.

Development of contractile dysfunction in rat heart failure: hierarchy of cellular events

2007 ◽  
Vol 293 (1) ◽  
pp. R284-R292 ◽  
Author(s):  
Marcel C. G. Daniels ◽  
Taihei Naya ◽  
Veronica L. M. Rundell ◽  
Pieter P. de Tombe
Keyword(s):  
Heart Failure ◽  
Atp Hydrolysis ◽  
Early Stage ◽  
Left Ventricular ◽  
Hydrolysis Rate ◽  
Cellular Mechanisms ◽  
Twitch Force ◽  
Protein Levels ◽  
Cellular Events ◽  
End Stage

The cellular mechanisms underlying the development of congestive heart failure (HF) are not well understood. Accordingly, we studied myocardial function in isolated right ventricular trabeculae from rats in which HF was induced by left ventricular myocardial infarction (MI). Both early-stage (12 wk post-MI; E-pMI) and late, end-stage HF (28 wk post-Mi; L-pMI) were studied. HF was associated with decreased sarcoplasmic reticulum Ca2+ ATPase protein levels (28% E-pMI; 52% L-pMI). HF affected neither sodium/calcium exchange, ryanodine receptor, nor phospholamban protein levels. Twitch force at saturating extracellular [Ca2+] was depressed in HF (30% E-pMI; 38% L-pMI), concomitant with a marked increase in sensitivity of twitch force toward extracellular [Ca2+] (26% E-pMI; 68% L-pMI). Ca2+-saturated myofilament force development in skinned trabeculae was unchanged in E-pMI but significantly depressed in L-pMI (45%). Tension-dependent ATP hydrolysis rate was depressed in L-pMI (49%), but not in E-pMI. Our results suggest a hierarchy of cellular events during the development of HF, starting with altered calcium homeostasis during the early phase followed by myofilament dysfunction at end-stage HF.

scholarly journals Constitutive overexpression of phosphomimetic phospholemman S68E mutant results in arrhythmias, early mortality, and heart failure: potential involvement of Na+/Ca2+ exchanger

2012 ◽  
Vol 302 (3) ◽  
pp. H770-H781 ◽  
Author(s):  
Jianliang Song ◽  
Erhe Gao ◽  
JuFang Wang ◽  
Xue-Qian Zhang ◽  
Tung O. Chan ◽  
...  
Keyword(s):  
Action Potential ◽  
Ventricular Arrhythmias ◽  
Left Ventricular ◽  
Resting Membrane Potential ◽  
Protein Levels ◽  
Disease States ◽  
Plasmic Reticulum ◽  
Lv Mass ◽  
Intracellular Ca ◽  
Constitutive Overexpression

Expression and activity of cardiac Na+/Ca2+ exchanger (NCX1) are altered in many disease states. We engineered mice in which the phosphomimetic phospholemman S68E mutant (inhibits NCX1 but not Na+-K+-ATPase) was constitutively overexpressed in a cardiac-specific manner (conS68E). At 4–6 wk, conS68E mice exhibited severe bradycardia, ventricular arrhythmias, increased left ventricular (LV) mass, decreased cardiac output (CO), and ∼50% mortality compared with wild-type (WT) littermates. Protein levels of NCX1, calsequestrin, ryanodine receptor, and α1- and α2-subunits of Na+-K+-ATPase were similar, but sarco(endo)plasmic reticulum Ca2+-ATPase was lower, whereas L-type Ca2+ channels were higher in conS68E hearts. Resting membrane potential and action potential amplitude were similar, but action potential duration was dramatically prolonged in conS68E myocytes. Diastolic intracellular Ca2+ ([Ca2+]i) was higher, [Ca2+]i transient and maximal contraction amplitudes were lower, and half-time of [Ca2+]i transient decline was longer in conS68E myocytes. Intracellular Na+ reached maximum within 3 min after isoproterenol addition, followed by decline in WT but not in conS68E myocytes. Na+/Ca2+ exchange, L-type Ca2+, Na+-K+-ATPase, and depolarization-activated K+ currents were decreased in conS68E myocytes. At 22 wk, bradycardia and increased LV mass persisted in conS68E survivors. Despite comparable baseline CO, conS68E survivors at 22 wk exhibited decreased chronotropic, inotropic, and lusitropic responses to isoproterenol. We conclude that constitutive overexpression of S68E mutant was detrimental, both in terms of depressed cardiac function and increased arrhythmogenesis.

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