Deoxyglucose and reduced glutathione mimic effects of hypoxia on K+ and Ca2+ conductances in pulmonary artery cells

1994 ◽  
Vol 267 (1) ◽  
pp. L52-L63 ◽  
Author(s):  
X. J. Yuan ◽  
M. L. Tod ◽  
L. J. Rubin ◽  
M. P. Blaustein
Keyword(s):  
Pulmonary Artery ◽  
Action Potentials ◽  
Reduced Glutathione ◽  
Metabolic Inhibitors ◽  
Common Mechanism ◽  
Pipette Solution ◽  
Voltage Gated ◽  
Kv Channels ◽  
Channel Inhibition ◽  
Ca2 Channels

Hypoxia-induced pulmonary vasoconstriction (HPV) is triggered by a rise in cytosolic Ca2+ concentration ([Ca2+]i) that is partially controlled by voltage-gated Ca2+ channels. Hypoxia inhibits voltage-gated K+ (KV) channels in pulmonary artery (PA) myocytes. This depolarizes the cells, opens voltage-gated Ca2+ channels, thereby increases [Ca2+]i, and initiates HPV. In intact animals and isolated perfused lungs, metabolic inhibitors and reducing agents augment HPV. We compared the effects of hypoxia with the glycolysis inhibitor, 2-deoxy-D-glucose (2-DOG), and the reducing agent, reduced glutathione (GSH), on voltage-gated steady-state K+ currents (IK,ss) and membrane potential (Em) in cultured rat pulmonary and mesenteric arterial (MA) smooth muscle cells. Bath application of 10 mM 2-DOG (glucose-free) or 5-10 mM GSH reversibly reduced IK,ss by 25-35% in PA myocytes, with 5 mM ATP present in the pipette solution. Neither hypoxia nor 2-DOG significantly affected IK,ss in MA myocytes, but GSH did reduce IK,ss in these cells. Furthermore, hypoxia, 2-DOG, and GSH depolarized PA cells in the absence as well as in the presence of external Ca2+. Hypoxia, 2-DOG, and GSH also evoked action potentials on the top of the steady depolarization in 36-50% of PA myocytes but not in any MA myocytes; removal of external Ca2+ abolished the action potentials without affecting the steady depolarization. These effects were comparable to those produced by 4-aminopyridine (5-10 mM), a blocker of KV channels. This implies that the action potentials are attributable to Ca2+ influx through voltage-gated Ca2+ channels opened by the steady depolarization due to KV channel inhibition. In the presence of 2-DOG or GSH, hypoxia had no further effect on IK,ss or Em in PA cells; this implies that hypoxia, 2-DOG, and GSH all block the same K+ channels. The data suggest that 1) the hypoxia-induced decrease of IK,ss and the resultant depolarization in PA myocytes may be related to a local decrease of intracellular ATP level and/or a change in redox status of the membrane or cytosol and 2) extracellular Ca(2+)-dependent action potentials may be responsible for at least part of the increase in [Ca2+]i during HPV. Similarities between the effects of hypoxia, 2-DOG, and GSH on IK,ss and Em in PA myocytes, along with the dissimilar responses of PA and MA myocytes, suggest that a common mechanism may underlie the responses of PA cells to these treatments.

scholarly journals Membrane potential responses of paramecium caudatum to bitter substances: existence of multiple pathways for bitter responses

1998 ◽  
Vol 201 (1) ◽  
pp. 13-20
Author(s):  
K Oami
Keyword(s):  
Membrane Potential ◽  
Action Potentials ◽  
Bathing Solution ◽  
Transduction Pathway ◽  
Paramecium Caudatum ◽  
External Application ◽  
Common Component ◽  
Voltage Gated ◽  
Mutant Cells ◽  
Ca2 Channels

The membrane potential responses of Paramecium caudatum to the external application of bitter substances were examined by employing conventional electrophysiological techniques. Mutant cells defective in voltage-gated Ca2+ channels were used to record the potential responses in the absence of contamination by Ca2+ action potentials. The cells produced a transient depolarization followed by a transient hyperpolarization in response to a rapid whole-cell application of chloroquine, strychnine nitrate or brucine. Of these chemicals, chloroquine was the most potent. Cells produced a simple depolarization in response to a localized application of test chemicals to the anterior region, whereas they produced a transient hyperpolarization in response to an application to the posterior region. Membrane potential responses to an application of chloroquine declined with repeated application. The presence of chloroquine in the external bathing solution strongly inhibited the membrane potential responses to an application of brucine or strychnine. However, the presence of chloroquine did not affect the membrane potential responses to an application of quinine. It is suggested that chloroquine, strychnine and brucine share a common component of their transduction pathways, but that the transduction pathway for quinine is different.

K+ channel inhibition, calcium signaling, and vasomotor tone in canine pulmonary artery smooth muscle

2000 ◽  
Vol 279 (2) ◽  
pp. L242-L251 ◽  
Author(s):  
Shouzaburoh Doi ◽  
Derek S. Damron ◽  
Koji Ogawa ◽  
Satoru Tanaka ◽  
Mayumi Horibe ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Pulmonary Artery ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
K Channel ◽  
Voltage Gated ◽  
Channel Inhibition ◽  
Pulmonary Arterial ◽  
Pulmonary Artery Smooth Muscle

We investigated the role of K+ channels in the regulation of baseline intracellular free Ca2+ concentration ([Ca2+]i), α-adrenoreceptor-mediated Ca2+ signaling, and capacitative Ca2+ entry in pulmonary artery smooth muscle cells (PASMCs). Inhibition of voltage-gated K+ channels with 4-aminopyridine (4-AP) increased the membrane potential and the resting [Ca2+]i but attenuated the amplitude and frequency of the [Ca2+]i oscillations induced by the α-agonist phenylephrine (PE). Inhibition of Ca2+-activated K+ channels (with charybdotoxin) and inhibition (with glibenclamide) or activation of ATP-sensitive K+ channels (with lemakalim) had no effect on resting [Ca2+]i or PE-induced [Ca2+]i oscillations. Thapsigargin was used to deplete sarcoplasmic reticulum Ca2+ stores in the absence of extracellular Ca2+. Under these conditions, 4-AP attenuated the peak and sustained components of capacitative Ca2+ entry, which was observed when extracellular Ca2+ was restored. Capacitative Ca2+ entry was unaffected by charybdotoxin, glibenclamide, or lemakalim. In isolated pulmonary arterial rings, 4-AP increased resting tension and caused a leftward shift in the KCl dose-response curve. In contrast, 4-AP decreased PE-induced contraction, causing a rightward shift in the PE dose-response curve. These results indicate that voltage-gated K+ channel inhibition increases resting [Ca2+]i and tone in PASMCs but attenuates the response to PE, likely via inhibition of capacitative Ca2+entry.

Intracellular acidosis differentially regulates KV channels in coronary and pulmonary vascular muscle

1998 ◽  
Vol 275 (4) ◽  
pp. H1351-H1359 ◽  
Author(s):  
Marcie G. Berger ◽  
Christophe Vandier ◽  
Pierre Bonnet ◽  
William F. Jackson ◽  
Nancy J. Rusch
Keyword(s):  
Vascular Reactivity ◽  
Pulmonary Arteries ◽  
Cell Types ◽  
Resistance Arteries ◽  
Intracellular Acidosis ◽  
Pipette Solution ◽  
Voltage Gated ◽  
Kv Channels ◽  
Ionic Mechanisms ◽  
Induced Changes

Decreases in intracellular pH (pHi) potently dilate coronary resistance arteries but constrict small pulmonary arteries. To define the ionic mechanisms of these responses, this study investigated whether acute decreases in pHi differentially regulate K+ currents in single vascular smooth muscle (VSM) cells isolated from rat coronary and pulmonary resistance arteries. In patch-clamp studies, whole cell K+ currents were elicited by 10-mV depolarizing steps between −60 and 0 mV in VSM cells obtained from 50- to 150-μm-OD arterial branches, and pHi was lowered by altering the NH4Cl gradient across the cell membrane. Progressively lowering pHi from calculated values of 7.0 to 6.7 and 6.4 increased the peak amplitude of K+ current in coronary VSM cells by 15 ± 5 and 23 ± 3% but reduced K+ current in pulmonary VSM cells by 18 ± 3 and 21 ± 3%, respectively. These changes were reversed by returning cells to the control pHi of 7.0 and were eliminated by dialyzing cells with pipette solution containing 50 mmol/l HEPES to buffer NH4Cl-induced changes in pHi. Pharmacological block of ATP-sensitive K+ channels and Ca2+-activated K+ channels by 1 μmol/l glibenclamide and 100 nmol/l iberiotoxin, respectively, did not prevent changes in K+ current levels induced by acidotic pHi. However, block of voltage-gated K+ channels by 3 mmol/l 4-aminopyridine abolished acidosis-induced changes in K+ current amplitudes in both VSM cell types. Interestingly, α-dendrotoxin (100 nmol/l), which blocks only select subtypes of voltage-gated K+ channels, abolished the acidosis-induced decrease in K+current in pulmonary VSM cells but did not affect the acidosis-induced increase in K+ current observed in coronary VSM cells. These findings suggest that opposing, tissue-specific effects of pHi on distinct subtypes of voltage-gated K+ channels in coronary and pulmonary VSM membranes may differentially regulate vascular reactivity in these two circulations under conditions of acidotic stress.

scholarly journals Adrenaline Stimulates Glucagon Secretion in Pancreatic A-Cells by Increasing the Ca2+ Current and the Number of Granules Close to the L-Type Ca2+ Channels

1997 ◽  
Vol 110 (3) ◽  
pp. 217-228 ◽  
Author(s):  
Jesper Gromada ◽  
Krister Bokvist ◽  
Wei-Guang Ding ◽  
Sebastian Barg ◽  
Karsten Buschard ◽  
...  
Keyword(s):  
Electrical Activity ◽  
Adrenergic Receptors ◽  
Action Potentials ◽  
Glucagon Secretion ◽  
Stimulatory Action ◽  
Voltage Gated ◽  
A Cells ◽  
Β Adrenergic Receptors ◽  
Ca2 Channels ◽  
Stimulation Of

We have monitored electrical activity, voltage-gated Ca2+ currents, and exocytosis in single rat glucagon-secreting pancreatic A-cells. The A-cells were electrically excitable and generated spontaneous Na+- and Ca2+-dependent action potentials. Under basal conditions, exocytosis was tightly linked to Ca2+ influx through ω-conotoxin-GVIA–sensitive (N-type) Ca2+ channels. Stimulation of the A-cells with adrenaline (via β-adrenergic receptors) or forskolin produced a greater than fourfold PKA-dependent potentiation of depolarization-evoked exocytosis. This enhancement of exocytosis was due to a 50% enhancement of Ca2+ influx through L-type Ca2+ channels, an effect that accounted for <30% of the total stimulatory action. The remaining 70% of the stimulation was attributable to an acceleration of granule mobilization resulting in a fivefold increase in the number of readily releasable granules near the L-type Ca2+ channels.

scholarly journals Genomic Action of Sigma-1 Receptor Chaperone Relates to Neuropathic Pain

2021 ◽  
Author(s):  
Shao-Ming Wang ◽  
Nino Goguadze ◽  
Yuriko Kimura ◽  
Yuko Yasui ◽  
Bin Pan ◽  
...  
Keyword(s):  
Neuropathic Pain ◽  
Action Potentials ◽  
Neuronal Excitability ◽  
Mrna Translation ◽  
Sigma 1 Receptor ◽  
Voltage Gated ◽  
Sigma 1 ◽  
Frequency Of Action Potentials ◽  
Translational Inhibitor ◽  
Ca2 Channels

AbstractSigma-1 receptors (Sig-1Rs) are endoplasmic reticulum (ER) chaperones implicated in neuropathic pain. Here we examine if the Sig-1R may relate to neuropathic pain at the level of dorsal root ganglia (DRG). We focus on the neuronal excitability of DRG in a “spare nerve injury” (SNI) model of neuropathic pain in rats and find that Sig-1Rs likely contribute to the genesis of DRG neuronal excitability by decreasing the protein level of voltage-gated Cav2.2 as a translational inhibitor of mRNA. Specifically, during SNI, Sig-1Rs translocate from ER to the nuclear envelope via a trafficking protein Sec61β. At the nucleus, the Sig-1R interacts with cFos and binds to the promoter of 4E-BP1, leading to an upregulation of 4E-BP1 that binds and prevents eIF4E from initiating the mRNA translation for Cav2.2. Interestingly, in Sig-1R knockout HEK cells, Cav2.2 is upregulated. In accordance with those findings, we find that intra-DRG injection of Sig-1R agonist (+)pentazocine increases frequency of action potentials via regulation of voltage-gated Ca2+ channels. Conversely, intra-DRG injection of Sig-1R antagonist BD1047 attenuates neuropathic pain. Hence, we discover that the Sig-1R chaperone causes neuropathic pain indirectly as a translational inhibitor.

A model for dendritic Ca2+ accumulation in hippocampal pyramidal neurons based on fluorescence imaging measurements

1994 ◽  
Vol 71 (3) ◽  
pp. 1065-1077 ◽  
Author(s):  
D. B. Jaffe ◽  
W. N. Ross ◽  
J. E. Lisman ◽  
N. Lasser-Ross ◽  
H. Miyakawa ◽  
...  
Keyword(s):  
Fluorescence Imaging ◽  
Action Potentials ◽  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Na Channels ◽  
Hippocampal Pyramidal Neurons ◽  
K Channels ◽  
Voltage Gated ◽  
Synaptic Potentials ◽  
Ca2 Channels

1. High-speed fluorescence imaging was used to measure intracellular Ca2+ concentration ([Ca2+]i) changes in hippocampal neurons injected with the Ca(2+)-sensitive indicator fura-2 during intrasomatic and synaptic stimulation. The results of these experiments were used to construct a biophysical model of [Ca2+]i dynamics in hippocampal neurons. 2. A compartmental model of a pyramidal neuron was constructed incorporating published passive membrane properties of these cells, three types of voltage-gated Ca2+ channels characterized from adult hippocampal neurons, voltage-gated Na+ and K+ currents, and mechanisms for Ca2+ buffering and extrusion. 3. In hippocampal pyramidal neurons imaging of Na+ entry during electrical activity suggests that Na+ channels, at least in sufficient density to sustain action potentials, are localized in the soma and the proximal part of the apical dendritic tree. The model, which incorporates this distribution, demonstrates that action potentials attenuate steeply in passive distal dendritic compartments or distal dendritic compartments containing Ca2+ and K+ channels. This attenuation was affected by intracellular resistivity but not membrane resistivity. 4. Consistent with fluorescence imaging experiments, a non-uniform distribution of Ca2+ accumulation was generated by Ca2+ entry through voltage-gated Ca2+ channels opened by decrementally propagating Na+ action potentials. Consequently, the largest increases in [C2+]i were produced in the proximal dendrites. Distal voltage-gated Ca2+ currents were activated by broad, almost isopotential action potentials produced by reducing the overall density of K+ channels. 5. Simulations of subthreshold synaptic stimulation produced dendritic Ca2+ entry by the activation of voltage-gated Ca2+ channels. In the model these Ca2+ signals were localized near the site of synaptic input because of the attenuation of synaptic potentials with distance from the site of origin and the steep voltage-dependence of Ca2+ channel activation. 6. These simulations support the hypotheses generated from experimental evidence regarding the differential distribution of voltage-gated Ca2+ and Na+ channels in hippocampal neurons and the resulting voltage-gated Ca2+ accumulation from action and synaptic potentials.

Enhanced ETA-receptor-mediated inhibition of Kv channels in hypoxic hypertensive rat pulmonary artery myocytes

1999 ◽  
Vol 277 (1) ◽  
pp. H363-H370 ◽  
Author(s):  
Kai-Xun Li ◽  
Brian Fouty ◽  
Ivan F. McMurtry ◽  
David M. Rodman
Keyword(s):  
Pulmonary Hypertension ◽  
Pulmonary Artery ◽  
Hypoxic Pulmonary Hypertension ◽  
Voltage Gated ◽  
Receptor Coupling ◽  
Kv Channels ◽  
Whole Cell Patch Clamp ◽  
Intracellular Ca ◽  
Eta Receptor

Endothelin (ET)-1 has been implicated as a critical mediator in the pathogenesis of hypoxic pulmonary hypertension. We questioned whether, during exposure to chronic hypobaric hypoxia, rat pulmonary artery smooth muscle cells (PASMC) became sensitized to ET-1. Two effects of ET-1, inhibition of voltage-gated K+(Kv) channels and release of intracellular Ca2+, were studied using whole cell patch clamp and single cell indo 1 fluorescence, respectively. In both normotensive and chronically hypoxic-hypertensive PASMC, ET-1 caused concentration-dependent inhibition of voltage-gated K+ current [ I K(v)], with maximum inhibition of 12–18% seen at a concentration of 0.1–1 nM. Although the chronically hypoxic-hypertensive PASMC was no more susceptible to ET-1-mediated I K(v) inhibition, a switch in coupling between ET-1 and I K(v) from ETB to ETA receptors occurred. This switch in receptor coupling, combined with reduced I K(v) density and increased ET-1 production in the hypoxic rat lung, may help explain the ability of ETA-receptor blockers to attenuate the development of hypoxic pulmonary hypertension in vivo.

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