Functional and molecular identification of ERG channels in murine portal vein myocytes

2002 ◽  
Vol 283 (3) ◽  
pp. C866-C877 ◽  
Author(s):  
Susumu Ohya ◽  
Burton Horowitz ◽  
Iain A. Greenwood
Keyword(s):  
Portal Vein ◽  
Contractile Activity ◽  
Membrane Conductance ◽  
Cell Voltage ◽  
Mean Amplitude ◽  
Isometric Tension ◽  
Real Time Quantitative Pcr ◽  
Inward Currents ◽  
Portal Veins ◽  
Rapid Kinetics

Ion channels encoded by ether-à-go-go-related genes (ERG) have been implicated in repolarization of the cardiac action potential and also as components of the resting membrane conductance in various cells. The aim of the present study was to determine whether ERG channels were expressed in smooth muscle cells isolated from portal vein. RT-PCR demonstrated the expression of murine ERG (mERG), and real-time quantitative PCR showed that the mERG1b isoform predominated over the mERG1a, mERG2, and mERG3 in portal vein. Single myocytes from portal vein displayed membrane staining with an ERG1-specific antibody. Whole cell voltage-clamp experiments were performed to determine whether portal vein myocytes expressed functional ERG channels. Large inward currents with distinctive kinetics were elicited that were inhibited rapidly by E-4031 (mean amplitude of the E-4031-sensitive current at −120 mV was −205 ± 24 pA; n = 14). Deactivation of the E-4031-sensitive current was voltage dependent (mean time constants at −80 and −120 mV were 103 ± 9 and 33 ± 2 ms, respectively; n = 13). Because of the rapid kinetics of mERG currents at more negative potentials, there was a substantial noninactivating “window” current that reached a maximum of −66 ± 10 pA at −70 mV. Complete portal veins exhibited spontaneous contractile activity in isometric tension experiments, and this activity was modified significantly by E-4031. These data show that ERG channels are expressed in murine portal vein myocytes that may contribute to the resting membrane conductance.

Effect of human plasma proteins on spontaneous contractile activity of rat mesenteric portal vein

1990 ◽  
Vol 68 (6) ◽  
pp. 737-743 ◽  
Author(s):  
G. Pillai ◽  
M. C. Sutter
Keyword(s):  
Portal Vein ◽  
Spontaneous Activity ◽  
Plasma Proteins ◽  
Mechanical Response ◽  
Contractile Activity ◽  
Physiological Salt Solution ◽  
Portal Veins ◽  
6 Hydroxydopamine ◽  
Dose Dependent Increase ◽  
Dose Dependent

This study examines the effect of various plasma proteins from man on the spontaneous contractile activity of the rat portal vein. Albumin, γ-globulin, α-globulin, β-globulin (the major plasma proteins), and immunoglobulin IgG (the major immunoglobulin present in the γ-globulin fraction) were obtained commercially. Mesenteric portal vein strips were prepared from rats and placed in a physiological salt solution in muscle baths for the measurement of longitudinal mechanical response. Portal veins exposed to albumin or γ-globulin showed a dose-dependent increase in the spontaneous activity, whereas those exposed to α-globulin or α - and β-globulin together showed a dose-dependent inhibition of spontaneous activity. Immunoglobulin IgG produced a dose-dependent increase in the spontaneous activity similar to that of γ-globulin. The increased spontaneous activity produced by albumin was not prevented by ouabain but was inhibited by phentolamine. Spontaneous contractile activity was stimulated by albumin in the chemically (6-hydroxydopamine) denervated portal vein. These findings indicate that albumin acts in a manner similar to noradrenaline. The increased spontaneous activity caused by γ-globulin (IgG) was inhibited by ouabain or verapamil. The effect of IgG was not dependent on α-adrenergic, cholinergic, histaminergic, serotoninergic, or renin angiotensin systems nor was it affected by removal of the endothelium. These observations may have implications in the pathophysiology of essential hypertension.Key words: vasomotion, mesenteric portal vein, plasma proteins, albumin, γ-globulin, inhibitory factor, stimulatory factor, IgG.

Vasomotion and Contraction in the Perfused Mesenteric–Portal Vein: Effect of Drugs and Altered Perfusion Pressure

1971 ◽  
Vol 49 (6) ◽  
pp. 615-618 ◽  
Author(s):  
H. James Rhodes ◽  
M. C. Sutter
Keyword(s):  
Portal Vein ◽  
Perfusion Pressure ◽  
Splanchnic Circulation ◽  
Intraluminal Pressure ◽  
Longitudinal Tension ◽  
Portal Veins ◽  
Spontaneous Contractions

Isolated rabbit anterior mesenteric–portal veins (A.M.V.) which possess vasomotion were perfused with Kreb's solution in an apparatus designed so that intraluminal pressure and longitudinal tension could be measured simultaneously. The rate of vasomotion increased as perfusion pressure was increased from 0 to approximately 5 or 6 mm Hg. The amplitude of these spontaneous contractions increased to a maximum at a perfusion pressure of approximately 6 mm Hg and then decreased as perfusion pressure was raised further. Noradrenaline (10−7 g/ml) increased the longitudinal tension, but slightly decreased intraluminal pressure. Isopropylnoradrenaline (10−7 g/ml) had little effect on intraluminal pressure but decreased the amplitude of spontaneous contractions. It is suggested that the effect of perfusion pressure on the frequency and amplitude of vasomotion in the A.M.V. is related to autoregulation and that this perfused preparation may be a useful model for study of the rheology and responses to drugs of the splanchnic circulation.

Oscillating Contractions in Protoplasmic Strands of Physarum: Mechanical and Thermal Methods of Phase Shifting for Studying the Nature of the Synchronizing Factor and its Transmission

1980 ◽  
Vol 85 (1) ◽  
pp. 21-31
Author(s):  
U. ACHENBACH ◽  
K. E. WOHLFARTH-BOTTERMANN
Keyword(s):  
Contractile Activity ◽  
Signal Transmission ◽  
Rapid Change ◽  
Isometric Tension ◽  
The Other ◽  
Rapid Phase ◽  
Thermal Methods ◽  
Original Length ◽  
Set Up ◽  
Rhythmic Contractile Activity

A new experimental investigation chamber was used to analyse the control of rhythmic contractile activity in Physarum. A strand was mounted in such a way that isometric tension measurements of contraction forces could be made on two regions independently, the two regions remaining connected. It was possible to disturb one region experimentally and to compare its behaviour with the other. A short time after being set up in the apparatus, the isometric contraction cycles in the two regions became synchronous. Stretching one region by 50% of its original length induced a phase delay relative to the other. A brief unilateral cold shock (Δt = 5舑15 °C) had a similar phase-retarding effect. Synchrony was subsequently reattained, unless the connecting region was cut or, for example, treated with 30 mM benzamide. In approximately 25% of the investigated strands, a rapid change to a higher temperature (Δt = 2舑5 °C) caused the warmed side to be phase-advanced. However, 75% of the strands did not show a phase shift, suggesting that a rapid phase regulation is supported by increased temperature. The described experimental assay is suitable for analysing the pathway and the nature of signal transmission in plasmodial strands. Note: Partly presented at the International Titisee-Conference on Cellular Oscillators, 22舑24 March 1979 (see J. exp. Biol. (1979)).

Tumoural portal vein thrombosis

1997 ◽  
Vol 38 (5) ◽  
pp. 655-659
Author(s):  
L. Marti-Bonmati ◽  
E. Lonjedo ◽  
D. Mathieu ◽  
C. Coffin ◽  
C. Poyatos ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Portal Vein ◽  
Imaging Techniques ◽  
Vena Cava ◽  
Tumour Thrombus ◽  
Vein Thrombosis ◽  
Significant Difference ◽  
Before And After ◽  
Portal Veins ◽  
Cellular Carcinoma

Purpose: Intrahepatic thrombus is usually associated with either cirrhosis or hepato-cellular carcinoma (HCC). Most HCCs enhance after the administration of MnDPDP (Teslascan). Our objective was to analyze the enhancement characteristics of tumour portal vein thrombi. Material and Methods: Thrombi affecting the main or segmental portal veins (17 cases) and the suprahepatic inferior vena cava (1 case) were retrospectively selected from a series of 128 patients studied with MR imaging before and after the administration of MnDPDP. Enhancement was assessed qualitatively and quantitatively. Results: All tumour thrombi enhanced after MnDPDP administration. The enhancement was more conspicuous in the GRE images. On the quantitative evaluation, the portal thrombus enhancement was greater for GRE images than SE images. Portal thrombi enhanced more than the liver and the HCCs. There was a significant difference between the enhancement of the HCCs and the thrombi with both MR imaging techniques. Conclusion: The greater enhancement of the tumour thrombus associated with the liver and HCC may suggest that other mechanisms, apart from accumulation of the contrast medium within the hepatocytes inside the thrombi, are involved in thrombus enhancement.

Voltage-dependent modulation of GABAA receptor channel desensitization in rat hippocampal neurons

1994 ◽  
Vol 71 (6) ◽  
pp. 2151-2160 ◽  
Author(s):  
K. W. Yoon
Keyword(s):  
Membrane Potential ◽  
Hippocampal Neurons ◽  
Membrane Conductance ◽  
Cell Voltage ◽  
Chloride Conductance ◽  
Membrane Voltage ◽  
Hippocampal Cell Culture ◽  
Voltage Dependent ◽  
Agonist Concentration ◽  
Rate Of Recovery

1. The mechanism of the time-dependent decline in gamma-amino-butyric acid (GABA)-induced chloride conductance, referred to as desensitization, was studied in dissociated rat hippocampal cell culture with the use of a whole-cell voltage-clamp recording. 2. In most cells the gradual decline of membrane conductance was dependent simultaneously on the agonist concentration and membrane voltage. Even in the continued presence of GABA, desensitization could be prevented by holding the membrane potential > 0 mV in a near symmetrical chloride gradient across the cell membrane. 3. The “recovery” from desensitization occurred after removal of the agonist with a time constant of approximately 35 s. The rate of recovery from desensitization was independent of membrane voltage. 4. When the membrane potential was jumped from a negative to a positive membrane potential during steady state of desensitization, the GABA-induced chloride conductance gradually “relaxed” to the undesensitized state. This phenomenon of gradual increase in chloride conductance or “reactivation” from desensitization was both voltage and agonist dependent. 5. The process of recovery of the GABA ionophore from the desensitized state is distinct from the process of reactivation, which is dependent both on the voltage and agonist. 6. These observations suggest that the ligand-bound GABA receptor has two alternate states, i.e., permissive (activated) and desensitized. The rates of transition between these two states are voltage dependent.

scholarly journals Prevention of Gut Barrier Dysfunction During Acute Massive Blood Loss (Experimental Study)

2019 ◽  
Vol 15 (4) ◽  
pp. 76-87
Author(s):  
A. Y. Yakovlev ◽  
G. A. Boyarinov ◽  
D. V. Ryabikov ◽  
M. A. Ryabikova ◽  
D. M. Protasov ◽  
...  
Keyword(s):  
Blood Loss ◽  
Portal Vein ◽  
Mucous Membrane ◽  
Systemic Circulation ◽  
Barrier Dysfunction ◽  
Gut Barrier ◽  
Massive Blood Loss ◽  
Weight Growth ◽  
Series Of Experiments ◽  
Portal Veins

Purpose of the study: to investigate the influence of hypovolemia correction by infusion of malate-containing preparations and subsequent glutamine-enriched nutritional support on the maintenance of gut barrier and overhydration in animals with acute massive blood loss/  Materials and methods. Blood samples were harvested from the tail and portal veins of rats (n=100) at different time points after the acute blood loss (>30% V/V) . Bacterial blood cultures for growth, lipopolysaccharide and presepsin concentrations, colon structures and animal weight were analyzed in blood and plasma specimens 1 hour, one day and 3 days after the hypovolemia correction. To correct the hypovolemia, in the 1st series of experiments, the Ringer’s solution and standard nutrient mixture were used; in the 2nd series malatecontaining solution and standard nutrient mixture were administered; in the 3rd series a malate-containing solution and glutamine-enriched nutrient mixture were employed.Results. In the portal vein blood of intact animals, endotoxin measurement was equal to 17.8Ѓ}3.9 pg/ml, that of presepsin — 405.6Ѓ}80.1 pg/ml. At all stages, tail and portal blood bacterial cultures were negative demonstrating an absence of bacterial growth and gut barrier intactness for live microorganisms. One hour after hypovolemia correction and blood reinfusion, multifold increase in endotoxin concentration in the blood from both portal and tail veins was accompanied by significant increase of presepsin concentration. 24 hours after the blood loss, in the animals of the 2nd and 3rd series, the levels of endotoxin, presepsin, and edema of the colon mucous membrane and submucosal space has become lower than those in the 1st series. Three days later, the advantages of glutamine-containing nutrition in the 3rd series of the experiment were determined that revealed decreasing the endotoxin and presepsin concentrations in the portal and tail vein blood and diminishing the levels of interstitial edema of colon and animal weight growth.Conclusion. Administration of malate-containing infusion preparations and glutamine-enriched nutrition after an acute massive blood loss contributes to decreasing presepsin production in GIT organs, abrogating endotoxin translocation into the portal vein and systemic circulation, lessening severity of edema of the mucous membrane and submucosal space of the colon, and reducing the previously increased animal body mass.

Membrane currents, contractions, and aftercontractions in cardiac Purkinje fibers

1982 ◽  
Vol 243 (1) ◽  
pp. H77-H86 ◽  
Author(s):  
S. L. Lipsius ◽  
W. R. Gibbons
Keyword(s):  
Outward Current ◽  
Membrane Conductance ◽  
Isometric Tension ◽  
Membrane Current ◽  
Membrane Currents ◽  
Purkinje Fibers ◽  
Cardiac Purkinje Fibers ◽  
And Behavior ◽  
Normal Calcium ◽  
Current Behavior

We examined relationships between isometric tension and membrane currents in sheep Purkinje fibers voltage clamped by the two-microelectrode method. Oscillatory restitution of contractility was accompanied by a small oscillation in membrane current and by an aftercontraction. The membrane current oscillation resembled the transient inward current (TI) others have reported in the presence of strophanthidin. Twitches produced by voltage clamp depolarizations did not correlate with net outward current in normal solution, but when the early outward current was blocked by 0.5 mM 4-aminopyridine, the residual outward current did correlate with twitches elicited by strong depolarizing clamps, particularly in solutions containing higher than normal calcium concentrations. The results illustrate important similarities and differences between membrane current behavior in sheep Purkinje fibers and behavior others have reported in calf fibers. Correlations between restitution, aftercontractions, and TI's, and between twitch tension and a component of outward current, may arise because of calcium regulation of membrane conductance, electrogenic Na-Ca exchange, or a combination of these and other mechanisms.

G proteins activate ionic conductances at multiple sites in T84 cells

1997 ◽  
Vol 272 (4) ◽  
pp. C1222-C1231
Author(s):  
L. Izu ◽  
M. Li ◽  
R. DeMuro ◽  
M. E. Duffey
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Cell Voltage ◽  
Equilibrium Potential ◽  
T84 Cells ◽  
Ionic Conductances ◽  
Inward Currents ◽  
Cl Channels ◽  
K Current

We examined the role of G proteins in activation of ionic conductances in isolated T84 cells during cholinergic stimulation. When cells were whole cell voltage clamped to the K+ equilibrium potential (E(K)) or Cl- equilibrium potential (E(Cl)) under standard conditions, the cholinergic agonist, carbachol, induced a large oscillating K+ current but only a small inward current. Addition of the GDP analogue, guanosine 5'-O-(2-thiodiphosphate), to pipettes blocked the ability of carbachol to activate the K+ current. Addition of the nonhydrolyzable GTP analogue, guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS), to pipettes stimulated large oscillating K+ and inward currents. This occurred even when Ca2+ was absent from the bath but not when the Ca2+ chelator, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, was added to pipettes. When all pipette and bath K+ was replaced with Na+ and cells were voltage clamped between E(Na) and E(Cl), GTPgammaS activated oscillating Na+ and Cl- currents. Finally, addition of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] to pipettes activated large oscillating K+ currents but only small inward currents. These results suggest that a carbachol-induced release of Ca2+ from intracellular stores is activated by a G protein through the phospholipase C-Ins(1,4,5)P3 signaling pathway. In addition, this or another G protein activates Cl- current by directly gating Cl- channels to increase their sensitivity to Ca2+.

scholarly journals β3-Adrenoceptor agonists inhibit purinergic receptor-mediated contractions of the murine detrusor

2019 ◽  
Vol 317 (1) ◽  
pp. C131-C142 ◽  
Author(s):  
Zhihui Fong ◽  
Caoimhín S. Griffin ◽  
Mark A. Hollywood ◽  
Keith D. Thornbury ◽  
Gerard P. Sergeant
Keyword(s):  
Purinergic Receptor ◽  
Isometric Tension ◽  
P2x Receptor ◽  
Rt Pcr ◽  
Patch Clamp Technique ◽  
Real Time Quantitative Pcr ◽  
Cell Current ◽  
Adrenoceptor Agonists ◽  
Cyclase Activator ◽  
Adenylate Cyclase Activator

β3-Adrenoceptor (β3-AR) agonists are used to treat overactive bladder syndrome; however, their mechanism of action has not been determined. The aims of this study were to compare the effects of β3-AR agonists on cholinergic versus purinergic receptor-mediated contractions of the detrusor and to examine the mechanisms underlying inhibition of the purinergic responses by β3-AR agonists. Isometric tension recordings were made from strips of murine detrusor and whole cell current recordings were made from freshly isolated detrusor myocytes using the patch-clamp technique. Transcriptional expression of exchange protein directly activated by cAMP (EPAC) subtypes in detrusor strips was assessed using RT-PCR and real-time quantitative PCR. The β3-AR agonists BRL37344 and CL316243 (100 nM) inhibited cholinergic nerve-mediated contractions of the detrusor by 19 and 23%, respectively, but did not reduce contractions induced by the cholinergic agonist carbachol (300 nM). In contrast, BRL37344 and CL316243 inhibited purinergic nerve-mediated responses by 55 and 56%, respectively, and decreased the amplitude of contractions induced by the P2X receptor agonist α,β-methylene ATP by 40 and 45%, respectively. The adenylate cyclase activator forskolin inhibited purinergic responses, and these effects were mimicked by a combination of the PKA activator N6-monobutyryl-cAMP and the EPAC activator 8-pCPT-2′- O-methyl-cAMP-AM (007-AM). Application of ATP (1 μM) evoked reproducible P2X currents in isolated detrusor myocytes voltage-clamped at −60 mV. These responses were reduced in amplitude in the presence of BRL37344 and also by 007-AM. This study demonstrates that β3-AR agonists reduce postjunctional purinergic responses in the detrusor via a pathway involving activation of the cAMP effector EPAC.

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