Ionic mechanisms of excitation-induced regulation of Na+-K+-ATPase mRNA expression in isolated rat EDL muscle

2006 ◽  
Vol 290 (5) ◽  
pp. R1397-R1406 ◽  
Author(s):  
K. T. Murphy ◽  
W. A. Macdonald ◽  
M. J. McKenna ◽  
T. Clausen
Keyword(s):  
Electrical Stimulation ◽  
Membrane Depolarization ◽  
Pulse Trains ◽  
Force Transducers ◽  
A 23187 ◽  
Intracellular Ca ◽  
Ionic Mechanisms ◽  
Exercise Induced ◽  
Edl Muscle ◽  
Isolated Rat

This study investigated the effects of electrical stimulation on Na+-K+-ATPase isoform mRNA, with the aim to identify factors modulating Na+-K+-ATPase mRNA in isolated rat extensor digitorum longus (EDL) muscle. Interventions designed to mimic exercise-induced increases in intracellular Na+ and Ca2+ contents and membrane depolarization were examined. Muscles were mounted on force transducers and stimulated with 60-Hz 10-s pulse trains producing tetanic contractions three times at 10-min intervals. Ouabain (1.0 mM, 120 min), veratridine (0.1 mM, 30 min), and monensin (0.1 mM, 30 min) were used to increase intracellular Na+ content. High extracellular K+ (13 mM, 60 min) and the Ca2+ ionophore A-23187 (0.02 mM, 30 min) were used to induce membrane depolarization and elevated intracellular Ca2+ content, respectively. Muscles were analyzed for Na+-K+-ATPase α1–α3 and β1–β3 mRNA (real-time RT-PCR). Electrical stimulation had no immediate effect on Na+-K+-ATPase mRNA; however at 3 h after stimulation, it increased α1, α2, and α3 mRNA by 223, 621, and 892%, respectively ( P = 0.010), without changing β mRNA. Ouabain, veratridine, and monensin increased intracellular Na+ content by 769, 724, and 598%, respectively ( P = 0.001) but did not increase mRNA of any isoform. High intracellular K+ concentration elevated α1 mRNA by 160% ( P = 0.021), whereas A-23187 elevated α3 mRNA by 123% ( P = 0.035) but reduced β1 mRNA by 76% ( P = 0.001). In conclusion, electrical stimulation induced subunit-specific increases in Na+-K+-ATPase mRNA in isolated rat EDL muscle. Furthermore, Na+-K+-ATPase mRNA appears to be regulated by different stimuli, including cellular changes associated with membrane depolarization and increased intracellular Ca2+ content but not increased intracellular Na+ content.

Stimulatory effects of bilirubin on amylase release from isolated rat pancreatic acini

2002 ◽  
Vol 282 (2) ◽  
pp. G249-G256 ◽  
Author(s):  
Yoshihide Hirohata ◽  
Masatoshi Fujii ◽  
Yoshinori Okabayashi ◽  
Yoshikuni Nagashio ◽  
Mitsuo Tashiro ◽  
...  
Keyword(s):  
Etiologic Factor ◽  
Dependent Manner ◽  
Camp Content ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Kinase C ◽  
A 23187 ◽  
Intracellular Ca ◽  
Pancreatic Exocrine ◽  
Isolated Rat

Considered to be an etiologic factor of acute pancreatitis, hypersecretion of pancreatic juice and digestive enzymes is often associated with hyperbilirubinemia. We explored the intracellular mechanisms through which bilirubin affects pancreatic exocrine secretory function by examining the effect of bilirubin on isolated rat pancreatic acini. Bilirubin stimulated amylase release in a concentration- and time-dependent manner, significantly increasing amylase release at concentrations >5 mg/100 ml and after 15 min of incubation. Coincubation of bilirubin with vasoactive intestinal polypeptide, 8-bromo-cAMP, or A-23187 had a synergistic effect on amylase release, whereas coincubation with CCK-8, carbamylcholine, or 12- O-tetradecanoylphorbol 13-acetate had an additive effect. Bilirubin did not affect acinar cAMP content or Ca2+efflux. Intracellular Ca2+ pool depletion had no influence on bilirubin-evoked amylase release. The protein kinase C (PKC) inhibitors staurosporine and calphostin C partially but significantly inhibited bilirubin-stimulated amylase release, whereas the PKA inhibitor H-89 did not. The tyrosine kinase (TK) inhibitor genistein, phospholipase A2 (PLA2) inhibitor indoxam, and PLC inhibitor U-73122 also inhibited amylase release. Bilirubin significantly translocated PKC activity from the cytosol to the membrane fraction and activated TK in cytosol and membrane fractions. These results indicate that bilirubin stimulates amylase release by activating PKC and TK in rat pancreatic acini and that PLC and PLA2 partly mediate this process.

scholarly journals Attenuation of extracellular ATP response in cardiomyocytes isolated from hearts subjected to ischemia-reperfusion

2005 ◽  
Vol 289 (2) ◽  
pp. H614-H623 ◽  
Author(s):  
Harjot K. Saini ◽  
Vijayan Elimban ◽  
Naranjan S. Dhalla
Keyword(s):  
Cardiac Function ◽  
Positive Inotropic Effect ◽  
Ischemia Reperfusion ◽  
Cardiac Contractility ◽  
Extracellular Atp ◽  
Binding Characteristics ◽  
Rat Hearts ◽  
The Status ◽  
Intracellular Ca ◽  
Isolated Rat

Extracellular ATP is known to augment cardiac contractility by increasing intracellular Ca2+ concentration ([Ca2+]i) in cardiomyocytes; however, the status of ATP-mediated Ca2+ mobilization in hearts undergoing ischemia-reperfusion (I/R) has not been examined previously. In this study, therefore, isolated rat hearts were subjected to 10–30 min of global ischemia and 30 min of reperfusion, and the effect of extracellular ATP on [Ca2+]i was measured in purified cardiomyocytes by fura-2 microfluorometry. Reperfusion for 30 min of 20-min ischemic hearts, unlike 10-min ischemic hearts, revealed a partial depression in cardiac function and ATP-induced increase in [Ca2+]i; no changes in basal [Ca2+]i were evident in 10- or 20-min I/R preparations. On the other hand, reperfusion of 30-min ischemic hearts for 5, 15, or 30 min showed a marked depression in both cardiac function and ATP-induced increase in [Ca2+]i and a dramatic increase in basal [Ca2+]i. The positive inotropic effect of extracellular ATP was attenuated, and the maximal binding characteristics of 35S-labeled adenosine 5′-[γ-thio]triphosphate with crude membranes from hearts undergoing I/R was decreased. ATP-induced increase in [Ca2+]i in cardiomyocytes was depressed by verapamil and Cibacron Blue in both control and I/R hearts; however, this response in I/R hearts, unlike control hearts, was not affected by ryanodine. I/R-induced alterations in cardiac function and ATP-induced increase in [Ca2+]i were attenuated by treatment with an antioxidant mixture and by ischemic preconditioning. The observed changes due to I/R were simulated in hearts perfused with H2O2. The results suggest an impairment of extracellular ATP-induced Ca2+ mobilization in I/R hearts, and this defect appears to be mediated through oxidative stress.

Effect of Lamotrigine on the Ca2+-Sensing Cation Current in Cultured Hippocampal Neurons

2001 ◽  
Vol 86 (5) ◽  
pp. 2520-2526 ◽  
Author(s):  
Zhi-Gang Xiong ◽  
Xiang-Ping Chu ◽  
J. F. MacDonald
Keyword(s):  
Action Potentials ◽  
Hippocampal Neurons ◽  
Neuronal Excitability ◽  
Membrane Depolarization ◽  
Slow Inward Current ◽  
Calcium Sensing ◽  
Cation Current ◽  
Imaging Experiment ◽  
Intracellular Ca ◽  
Cultured Hippocampal Neurons

Concentrations of extracellular calcium ([Ca2+]e) in the CNS decrease substantially during seizure activity. We have demonstrated previously that decreases in [Ca2+]e activate a novel calcium-sensing nonselective cation (csNSC) channel in hippocampal neurons. Activation of csNSC channels is responsible for a sustained membrane depolarization and increased neuronal excitability. Our study has suggested that the csNSC channel is likely involved in generating and maintaining seizure activities. In the present study, the effects of anti-epileptic agent lamotrigine (LTG) on csNSC channels were studied in cultured mouse hippocampal neurons using patch-clamp techniques. At a holding potential of −60 mV, a slow inward current through csNSC channels was activated by a step reduction of [Ca2+]e from 1.5 to 0.2 mM. LTG decreased the amplitude of csNSC currents dose dependently with an IC50 of 171 ± 25.8 (SE) μM. The effect of LTG was independent of membrane potential. In the presence of 300 μM LTG, the amplitude of csNSC current was decreased by 31 ± 3% at −60 mV and 29 ± 2.9% at +40 mV ( P > 0.05). LTG depressed csNSC current without affecting the potency of Ca2+ block of the current (IC50 for Ca2+block of csNSC currents in the absence of LTG: 145 ± 18 μM; in the presence of 300 μM LTG: 136 ± 10 μM. n = 5, P > 0.05). In current-clamp recordings, activation of csNSC channel by reducing the [Ca2+]e caused a sustained membrane depolarization and an increase in the frequency of spontaneous firing of action potentials. LTG (300 μM) significantly inhibited csNSC channel-mediated membrane depolarization and the excitation of neurons. Fura-2 ratiometric Ca2+imaging experiment showed that LTG also inhibited the increase in intracellular Ca2+ concentration induced by csNSC channel activation. The effect of LTG on csNSC channels may partially contribute to its broad spectrum of anti-epileptic actions.

Intravascular pressure regulates local and global Ca2+ signaling in cerebral artery smooth muscle cells

2001 ◽  
Vol 281 (2) ◽  
pp. C439-C448 ◽  
Author(s):  
Jonathan H. Jaggar
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Laser Scanning ◽  
Muscle Cells ◽  
Membrane Depolarization ◽  
Wave Frequency ◽  
Current Frequency ◽  
Frequency Wave ◽  
Intracellular Ca ◽  
Intravascular Pressure

The regulation of intracellular Ca2+ signals in smooth muscle cells and arterial diameter by intravascular pressure was investigated in rat cerebral arteries (∼150 μm) using a laser scanning confocal microscope and the fluorescent Ca2+ indicator fluo 3. Elevation of pressure from 10 to 60 mmHg increased Ca2+spark frequency 2.6-fold, Ca2+ wave frequency 1.9-fold, and global intracellular Ca2+ concentration ([Ca2+]i) 1.4-fold in smooth muscle cells, and constricted arteries. Ryanodine (10 μM), an inhibitor of ryanodine-sensitive Ca2+ release channels, or thapsigargin (100 nM), an inhibitor of the sarcoplasmic reticulum Ca2+-ATPase, abolished sparks and waves, elevated global [Ca2+]i, and constricted pressurized (60 mmHg) arteries. Diltiazem (25 μM), a voltage-dependent Ca2+ channel (VDCC) blocker, significantly reduced sparks, waves, and global [Ca2+]i, and dilated pressurized (60 mmHg) arteries. Steady membrane depolarization elevated Ca2+ signaling similar to pressure and increased transient Ca2+-sensitive K+ channel current frequency e-fold for ∼7 mV, and these effects were prevented by VDCC blockers. Data are consistent with the hypothesis that pressure induces a steady membrane depolarization that activates VDCCs, leading to an elevation of spark frequency, wave frequency, and global [Ca2+]i. In addition, pressure induces contraction via an elevation of global [Ca2+]i, whereas the net effect of sparks and waves, which do not significantly contribute to global [Ca2+]i in arteries pressurized to between 10 and 60 mmHg, is to oppose contraction.

PGE2 triggers recovery of transmucosal resistance via EP receptor cross talk in porcine ischemia-injured ileum

2001 ◽  
Vol 281 (2) ◽  
pp. G375-G381 ◽  
Author(s):  
Anthony T. Blikslager ◽  
Susan M. Pell ◽  
Karen M. Young
Keyword(s):  
Cross Talk ◽  
Splice Variants ◽  
Camp Content ◽  
Ep Receptors ◽  
Ussing Chambers ◽  
A 23187 ◽  
Receptor Interactions ◽  
Intracellular Ca ◽  
Ep Receptor ◽  
Receptor Cross Talk

16,16-Dimethyl-PGE2 (PGE2) may interact with one of four prostaglandin type E (EP) receptors, which signal via cAMP (via EP2 or EP4 receptors) or intracellular Ca2+ (via EP1 receptors). Furthermore, EP3 receptors have several splice variants, which may signal via cAMP or intracellular Ca2+. We sought to determine the PGE2 receptor interactions that mediate recovery of transmucosal resistance ( R) in ischemia-injured porcine ileum. Porcine ileum was subjected to 45 min of ischemia, after which the mucosa was mounted in Ussing chambers. Tissues were pretreated with indomethacin (5 μM). Treatment with the EP1, EP2, EP3, and EP4 agonist PGE2 (1 μM) elevated R twofold and significantly increased tissue cAMP content, whereas the EP2 and EP4 agonist deoxy-PGE1 (1 μM) or the EP1 and EP3 agonist sulprostone (1 μM) had no effect. However, a combination of deoxy-PGE1 and sulprostone stimulated synergistic elevations in R and tissue cAMP content. Furthermore, treatment of tissues with deoxy-PGE1 and the Ca2+ ionophore A-23187 stimulated synergistic increases in R and cAMP, indicating that PGE2 triggers recovery of R via EP receptor cross talk mechanisms involving cAMP and intracellular Ca2+.

Effects of myostatin on the mechanical properties of muscles during repeated active lengthening in the mouse

2019 ◽  
Vol 44 (4) ◽  
pp. 381-388
Author(s):  
Danguole Satkunskiene ◽  
Aivaras Ratkevicius ◽  
Sigitas Kamandulis ◽  
Tomas Venckunas
Keyword(s):  
Mechanical Properties ◽  
Isometric Force ◽  
Muscle Stiffness ◽  
Repeated Loading ◽  
Relative Reduction ◽  
Muscle Type ◽  
Age Dependent ◽  
Exercise Induced ◽  
Edl Muscle ◽  
Early Phases

The aim of the present study was to investigate how myostatin dysfunction affects fast and slow muscle stiffness and viscosity during severe repeated loading. Isolated extensor digitorum longus (EDL) and soleus muscles of young adult female mice of the BEH (dysfunctional myostatin) and BEH+/+ (functional myostatin) strains were subjected to 100 contraction–stretching loading cycles during which contractile and mechanical properties were assessed. BEH mice exhibited greater exercise-induced muscle damage, although the effect was muscle- and age-dependent and limited to the early phases of simulated exercise. The relative reduction of the EDL muscle isometric force recorded during the initial 10–30 loading cycles was greater in BEH mice than in BEH+/+ mice and exceeded that of the soleus muscle of either strain. The induced damage was associated with lower muscle stiffness. The effects of myostatin on the mechanical properties of muscles depend on muscle type and maturity.

Oxidative burst and NO generation as initial response to ischemia in flow-adapted endothelial cells

2001 ◽  
Vol 280 (5) ◽  
pp. H2126-H2135 ◽  
Author(s):  
Yefim Manevich ◽  
Abu Al-Mehdi ◽  
Vladimir Muzykantov ◽  
Aron B. Fisher
Keyword(s):  
Endothelial Cells ◽  
Plasma Membrane ◽  
Oxidative Burst ◽  
Initial Response ◽  
Membrane Depolarization ◽  
No Synthase ◽  
Potential Production ◽  
Perfusion Chamber ◽  
Intracellular Ca ◽  
Static Conditions

Shear stress modulates endothelial physiology, yet the effect(s) of flow cessation is poorly understood. The initial metabolic responses of flow-adapted bovine pulmonary artery endothelial cells to the abrupt cessation of flow (simulated ischemia) was evaluated using a perfusion chamber designed for continuous spectroscopy. Plasma membrane potential, production of reactive O2 species (ROS), and intracellular Ca2+ and nitric oxide (NO) levels were measured with fluorescent probes. Within 15 s after flow cessation, flow-adapted cells, but not cells cultured under static conditions, showed plasma membrane depolarization and an oxidative burst with generation of ROS that was inhibited by diphenyleneiodonium. EGTA-inhibitable elevation of intracellular Ca2+ and NO were observed at ∼30 and 60 s after flow cessation, respectively. NO generation was decreased in the presence of inhibitors of NO synthase and calmodulin. Thus flow-adapted endothelial cells sense the altered hemodynamics associated with flow cessation and respond by plasma membrane depolarization, activation of NADPH oxidase, Ca2+ influx, and activation of Ca2+/calmodulin-dependent NO synthase. This signaling response is unrelated to cellular anoxia.

An immediate endothelial cell signaling response to lung ischemia

2001 ◽  
Vol 281 (4) ◽  
pp. L993-L1000 ◽  
Author(s):  
Chun Song ◽  
Abu B. Al-Mehdi ◽  
Aron B. Fisher
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Initial Response ◽  
Membrane Depolarization ◽  
Initial Increase ◽  
Amplex Red ◽  
Vascular Space ◽  
Endothelial Response ◽  
Intracellular Ca

Abrupt cessation of lung perfusion induces a rapid endothelial response that is not associated with anoxia but reflects loss of normal shear stress. This response includes membrane depolarization, H2O2generation, and increased intracellular Ca2+. We evaluated these parameters immediately upon nonhypoxic ischemia using fluorescence videomicroscopy to image in situ endothelial cells in isolated, ventilated rat lungs. Lungs labeled with 4-{2-[6-(dioctylamino)-2-naphthalenyl]ethenyl}1-(3-sulfopropyl)-pyridinium (di-8-ANEPPS; a membrane potential probe), Amplex Red (an extracellular H2O2probe), or fluo 3-AM (a Ca2+indicator) were subjected to control perfusion followed by global ischemia. Endothelial di-8-ANEPPS fluorescence increased significantly within the first second of ischemia and stabilized at 15 s, indicating membrane depolarization by ∼17 mV; depolarization was blocked by preperfusion with the K+channel agonist lemakalim. Increased H2O2, inhibitable by catalase, was detected in the vascular space at 1–2 s after the onset of ischemia. Increased intracellular Ca2+was detected 10–15 s after the onset of ischemia; the initial increase was inhibited by preperfusion with thapsigargin. Thus the temporal sequence of the initial response of endothelial cells in situ to loss of shear stress (i.e., ischemia) is as follows: membrane depolarization, H2O2release, and increased intracellular Ca2+.

Inhibition of Na+/H+exchange stimulates CCK secretion in STC-1 cells

1998 ◽  
Vol 275 (4) ◽  
pp. G689-G695
Author(s):  
Veronica Prpic ◽  
J. Gregory Fitz ◽  
Yu Wang ◽  
John R. Raymond ◽  
Maria N. Garnovskaya ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Cell Metabolism ◽  
Hormone Secretion ◽  
Membrane Depolarization ◽  
Ph Sensitive ◽  
Extracellular Medium ◽  
Voltage Dependent ◽  
Effects Of Ph ◽  
Intracellular Ca ◽  
Cck Release

It has been demonstrated that K+ channel regulation of membrane potential is critical for control of CCK secretion. Because certain K+ channels are pH sensitive, it was postulated that pH affects K+channel activity in the CCK-secreting cell line STC-1 and may participate in regulating CCK secretion. The present study examines the role of electroneutral Na+/H+exchange on extracellular acidification and hormone secretion. Treatment of STC-1 cells with the amiloride analog ethylisopropyl amiloride (EIPA) to inhibit Na+/H+exchange inhibited Na+-dependent H+ efflux and increased basal CCK secretion. Substituting choline for NaCl in the extracellular medium elevated basal intracellular Ca2+concentration and stimulated CCK release. Stimulatory effects on hormone secretion were blocked by the L-type Ca2+ channel blocker diltiazem, indicating that secretion was dependent on the influx of extracellular Ca2+. To determine whether the effects of EIPA and Na+ depletion were due to membrane depolarization, we tested graded KCl concentrations. The ability of EIPA to increase CCK secretion was inhibited by depolarization induced by 10–50 mM KCl in the bath. Maneuvers to lower intracellular pH (pHi), including reducing extracellular pH (pHo) to 7.0 or treatment with sodium butyrate, significantly increased CCK secretion. To examine whether pH directly affects membrane K+ permeability, we measured outward currents carried by K+, using whole cell patch techniques. K+ current was significantly inhibited by lowering pHo to 7.0. These effects appear to be mediated through changes in pHi, because intracellular dialysis with acidic solutions nearly eliminated current activity. These results suggest that Na+/H+exchange and membrane potential may be functionally linked, where inhibition of Na+/H+exchange lowers pHi and depolarizes the membrane, perhaps through inhibition of pH-sensitive K+ channels. In turn, K+ channel closure and membrane depolarization open voltage-dependent Ca2+ channels, leading to an increase in cytosolic Ca2+ and CCK release. The effects of pHi on K+ channels may serve as a potent stimulus for hormone secretion, linking cell metabolism and secretory functions.

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