Regional differences in cholinergic regulation of potassium current in feline esophageal circular smooth muscle

2005 ◽  
Vol 288 (6) ◽  
pp. G1233-G1240 ◽  
Author(s):  
Ahmad Muinuddin ◽  
Khurram Naqvi ◽  
Laura Sheu ◽  
Herbert Y. Gaisano ◽  
Nicholas E. Diamant
Keyword(s):  
Smooth Muscle ◽  
Receptor Antagonist ◽  
Regional Differences ◽  
Outward Current ◽  
Receptor Expression ◽  
Membrane Excitability ◽  
Patch Clamp Technique ◽  
Current Increase ◽  
Esophageal Body ◽  
Circular Smooth Muscle

Potassium channels are important contributors to membrane excitability in smooth muscles. There are regional differences in resting membrane potential and K+-channel density along the length of the feline circular smooth muscle esophagus. The aim of this study was to assess responses of K+-channel currents to cholinergic (ACh) stimulation along the length of the feline circular smooth muscle esophageal body. Perforated patch-clamp technique assessed K+-channel responses to ACh stimulation in isolated smooth muscle cells from the circular muscle layer of the esophageal body at 2 (distal)- and 4-cm (proximal) sites above the lower esophageal sphincter. Western immunoblots assessed ion channel and receptor expression. ACh stimulation produced a transient increase in outward current followed by inhibition of spontaneous transient outward currents. These ACh-induced currents were abolished by blockers of large-conductance Ca2+-dependent K+ channels (BKCa). Distal cells demonstrated a greater peak current density in outward current than cells from the proximal region and a longer-lasting outward current increase. These responses were abolished by atropine and the specific M3 receptor antagonist 4-DAMP but not the M1 receptor antagonist pirenzipine or the M2 receptor antagonist methoctramine. BKCa expression along the smooth muscle esophagus was similar, but M3 receptor expression was greater in the distal region. Therefore, ACh can differentially activate a potassium channel (BKCa) current along the smooth muscle esophagus. This activation probably occurs through release of intracellular calcium via an M3 pathway and has the potential to modulate the timing and amplitude of peristaltic contraction along the esophagus.

Nitric oxide mediates outward potassium currents in opossum esophageal circular smooth muscle

1996 ◽  
Vol 270 (6) ◽  
pp. G932-G938 ◽  
Author(s):  
J. Jury ◽  
K. R. Boev ◽  
E. E. Daniel
Keyword(s):  
Nitric Oxide ◽  
Smooth Muscle ◽  
Circular Muscle ◽  
Outward Current ◽  
Equilibrium Potential ◽  
Patch Clamp Technique ◽  
Pipette Solution ◽  
Whole Cell ◽  
Circular Smooth Muscle ◽  
Outward Currents

Single smooth muscle cells from the opossum body circular muscle were isolated and whole cell currents were characterized by the whole cell patch-clamp technique. When the cells were held at -50 mV and depolarized to 70 mV in 20-mV increments, initial small inactivating inward currents were evoked (-30 to 30 mV) followed by larger sustained outward currents. Depolarization from a holding potential of -90 mV evoked an initial fast inactivating outward current sensitive to 4-aminopyridine but not to high levels of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). The outward currents reversed near K+ equilibrium potential and were abolished when KCl was replaced by CsCl in the pipette solution. The sustained outward current was inhibited by quinine and cesium. High EGTA in the pipette solution reduced but did not abolish the sustained outward currents, suggesting that both Ca(2+)-dependent and -independent currents were evoked. The nitric oxide (NO)-releasing agents Sin-1 and sodium nitroprusside increased outward K+ currents. High levels of EGTA in the pipette solution abolished the increase in outward current induced by Sin-1. The presence of cyclopiazonic acid, an inhibitor of the sarcoplasmic reticulum (SR) Ca2+ pump, blocked the effects of NO-releasing agents. We conclude that NO release activates K+ outward currents in opossum esophagus circular muscle, which may depend on Ca2+ release from the SR stores.

Potassium current in circular smooth muscle of human jejunum activated by fenamates

1993 ◽  
Vol 265 (5) ◽  
pp. G873-G879 ◽  
Author(s):  
G. Farrugia ◽  
J. L. Rae ◽  
M. G. Sarr ◽  
J. H. Szurszewski
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Outward Current ◽  
Major Determinant ◽  
Flufenamic Acid ◽  
Blood Levels ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Circular Smooth Muscle ◽  
Normal Human

Thirty-eight cells, freshly isolated from circular smooth muscle of normal human jejunum obtained from nine patients undergoing weight-reduction surgery for morbid obesity, were patch clamped using a perforated patch-clamp technique. A highly potassium-selective voltage-dependent outward current was present in all cells. The current was carried by a 220-pS channel that activated near -75 mV and reached unit open probability at about +10 mV. Blockade of the current by quinidine (50 microM) and tetraethylammonium (25 mM) was accompanied by membrane depolarization to 0 to -3 mV, suggesting that this current was the major determinant of the membrane potential. Flufenamic and mefenamic acid at concentrations comparable with blood levels reached when these drugs are used in clinical therapy as nonsteroidal anti-inflammatory agents, activated the potassium outward current and hyperpolarized the membrane potential. The shift in the membrane potential for 250 microM flufenamic acid was -36 +/- 24 (SD) mV. Activation was rapid (seconds) and reversible. It was concluded that normal human jejunal circular smooth muscle cells have a highly potassium-selective outward current, which is the major determinant of the membrane potential and which is activated by fenamates.

scholarly journals Small-conductance Ca2+-dependent K+ channels activated by ATP in murine colonic smooth muscle

1997 ◽  
Vol 273 (6) ◽  
pp. C2010-C2021 ◽  
Author(s):  
S. D. Koh ◽  
G. M. Dick ◽  
K. M. Sanders
Keyword(s):  
Smooth Muscle ◽  
Pyridoxal Phosphate ◽  
Single Channel ◽  
Outward Current ◽  
Disulfonic Acid ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Outward Currents ◽  
Murine Colon ◽  
Small Conductance

The patch-clamp technique was used to determine the ionic conductances activated by ATP in murine colonic smooth muscle cells. Extracellular ATP, UTP, and 2-methylthioadenosine 5′-triphosphate (2-MeS-ATP) increased outward currents in cells with amphotericin B-perforated patches. ATP (0.5–1 mM) did not affect whole cell currents of cells dialyzed with solutions containing ethylene glycol-bis(β-aminoethyl ether)- N, N, N′, N′-tetraacetic acid. Apamin (3 × 10−7M) reduced the outward current activated by ATP by 32 ± 5%. Single channel recordings from cell-attached patches showed that ATP, UTP, and 2-MeS-ATP increased the open probability of small-conductance, Ca2+-dependent K+ channels with a slope conductance of 5.3 ± 0.02 pS. Caffeine (500 μM) enhanced the open probability of the small-conductance K+ channels, and ATP had no effect after caffeine. Pyridoxal phosphate 6-azophenyl-2′,4′-disulfonic acid tetrasodium (PPADS, 10−4 M), a nonselective P2 receptor antagonist, prevented the increase in open probability caused by ATP and 2-MeS-ATP. PPADS had no effect on the response to caffeine. ATP-induced hyperpolarization in the murine colon may be mediated by P2y-induced release of Ca2+ from intracellular stores and activation of the 5.3-pS Ca2+-activated K+ channels.

Nongenomic effects of progesterone on human intestinal smooth muscle cells

1996 ◽  
Vol 271 (2) ◽  
pp. G370-G376 ◽  
Author(s):  
K. Bielefeldt ◽  
L. Waite ◽  
F. M. Abboud ◽  
J. L. Conklin
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Ionic Currents ◽  
Calcium Currents ◽  
Intestinal Smooth Muscle ◽  
Calcium Signal ◽  
Membrane Excitability ◽  
Patch Clamp Technique ◽  
Nongenomic Effects

Previous experiments demonstrated that progesterone affects intestinal smooth muscle cells through genomic and nongenomic pathways. We hypothesized that the nongenomic effect was mediated by changes in membrane excitability. We studied the effects of progesterone and other steroid hormones on a human intestinal smooth muscle cell line, using the whole cell patch-clamp technique. Ionic currents were elicited through steps from -70 mV to various test potentials. Progesterone dose-dependently reduced calcium currents. The decrease in inward current was partly due to a shift in the steady-state inactivation to more hyperpolarized potentials. This effect did not involve gene transcription, since it was not blocked by the progesterone antagonist ZK-98-299. The progesterone analogue 5-beta-dihydroprogesterone also decreased calcium currents, whereas its stereoisomer, 5-alpha- dihydroprogesterone, did not affect the properties of voltage-sensitive ion channels. Similarly, estradiol and dexamethasone did not alter inward currents. We conclude that progestins exert their nongenomic effects on intestinal smooth muscle cells by decreasing calcium currents. The change in the calcium signal may contribute to the reduction in muscle contraction observed after progesterone.

Caveolin-1-deficient aortic smooth muscle cells show cell autonomous abnormalities in proliferation, migration, and endothelin-based signal transduction

2006 ◽  
Vol 290 (6) ◽  
pp. H2393-H2401 ◽  
Author(s):  
Ghada S. Hassan ◽  
Terence M. Williams ◽  
Philippe G. Frank ◽  
Michael P. Lisanti
Keyword(s):  
Signal Transduction ◽  
Smooth Muscle ◽  
Receptor Antagonist ◽  
Neointimal Hyperplasia ◽  
Receptor Expression ◽  
Nuclear Antigen ◽  
Induced Response ◽  
Adjacent Cell ◽  
Caveolin 1

We previously showed that ablation of caveolin-1 (Cav-1) gene expression in mice promotes neointimal hyperplasia in vivo, a phenomenon normally characterized by smooth muscle cell (SMC) migration and proliferation. Whether these defects are cell autonomous, i.e., due to loss of Cav-1 within SMCs or loss of Cav-1 expression in other adjacent cell types in vivo, remains unknown. Cav-1 has been shown to associate with receptors for many vasoactive factors on the SMC surface. Therefore, Cav-1 might be an important regulator of SMC proliferation, migration, and signal transduction. To mechanistically dissect the role of Cav-1 in SMC signaling, we isolated SMCs from the aortas (AoSMCs) of Cav-1-deficient (Cav-1−/−) mice and characterized these cells with respect to their proliferation, migration, and Ca2+ response to an important vasoactive factor, endothelin-1 (ET-1). 5-Bromo-2′-deoxyuridine incorporation and a wound-healing assay showed an increase in proliferation and migration rates in Cav-1−/− compared with wild-type (Cav-1+/+) AoSMCs. Cav-1−/− AoSMCs demonstrated upregulation of phosphorylated ERK1/2, cyclin D1, and proliferating cell nuclear antigen and reduced expression of the cyclin-dependent kinase inhibitor p27 Kip1. The Ca2+ response was examined in the presence of ET-1 and assessed by confocal microscopy with the Ca2+-sensitive fluorescent probe fluo 3. When treated with ET-1, Cav-1−/− AoSMCs exhibited a faster and larger increase in free intracellular Ca2+ than Cav-1+/+ cells. The ET-1-induced response in Cav-1−/− cells was mediated by the ETB receptor, as shown using the ETB receptor antagonist BQ-788 and the ETA receptor antagonist BQ-123. In Cav-1−/− cells, ETA receptor expression was reduced and ETB receptor expression was upregulated. Therefore, Cav-1 ablation increased the ET-1-induced Ca2+ response in SMCs by altering the type and expression level of the ET receptor (i.e., receptor isoform switching). These data suggest a novel regulatory role for Cav-1 in SMCs with respect to their proliferation, migration, and Ca2+-mediated signaling.

scholarly journals Gene therapy of Cav1.2 channel with VIP and VIP receptor agonists and antagonists: a novel approach to designing promotility and antimotility agents

2008 ◽  
Vol 295 (1) ◽  
pp. G187-G196 ◽  
Author(s):  
Xuan-Zheng Shi ◽  
Sushil K. Sarna
Keyword(s):  
Smooth Muscle ◽  
Protein Expression ◽  
Receptor Antagonist ◽  
Gene Transcription ◽  
Primary Cultures ◽  
Colonic Transit ◽  
Muscle Contractility ◽  
Receptor Agonists ◽  
Circular Smooth Muscle ◽  
Gene And Protein Expression

Recent findings show that the enteric neurotransmitter VIP enhances gene transcription of the α1C subunit of Cav1.2 (L-type) Ca2+ channels in the primary cultures of human colonic circular smooth muscle cells and circular smooth muscle strips. In this study, we investigated whether systemic infusion of VIP in intact animals enhances the gene transcription and protein expression of these channels to accelerate colonic transit. We also investigated whether similar systemic infusions of VPAC1/2 receptor antagonist retards colonic transit by repressing the constitutive gene expression of the α1C subunit. We found that the systemic infusion of VIP for 7 days by a surgically implanted osmotic pump enhances the gene and protein expression of the α1C subunit and circular muscle contractility in the proximal and the middle rat colons, but not in the distal colon. A similar systemic infusion of VPAC1/2 receptor antagonist represses the expression of the α1C subunit and circular smooth muscle contractility in the proximal and the middle colons. The VIP infusion accelerates colonic transit and pellet defecation by rats, whereas the infusion of VPAC1/2 receptor antagonist retards colonic transit and pellet defecation. VPAC1 receptors, but not VPAC2 receptors, mediate the above gene transcription-induced promotility effects of VIP. We conclude that VIP and VPAC1 receptor agonists may serve as potential promotility agents in constipation-like conditions, whereas VPAC receptor antagonists may serve as potential antimotility agents in diarrhea-like conditions produced by enhanced motility function.

scholarly journals Modulation of calcium channels in arterial smooth muscle cells by dihydropyridine enantiomers.

1993 ◽  
Vol 101 (3) ◽  
pp. 393-410 ◽  
Author(s):  
S Hering ◽  
A D Hughes ◽  
E N Timin ◽  
T B Bolton
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Pulse Train ◽  
Muscle Cells ◽  
Drug Action ◽  
Bay K 8644 ◽  
Patch Clamp Technique ◽  
Current Increase ◽  
Inactivation Curve ◽  
Mean Time

The actions of the optical enantiomers of BAY K 8644 and Sandoz 202,791 were studied on barium inward currents recorded using the whole-cell configuration of the patch clamp technique from enzymatically isolated smooth muscle cells from the rabbit ear artery. The enantiomers were applied by bath perfusion or rapidly by a concentration jump technique, which enabled the study of drug action under equilibrium and nonequilibrium conditions. A larger effect of agonists was seen on peak inward current in 110 mM Ba when small rather than large depolarizations were applied. The midpoint voltage of the steady-state inactivation curve of IBa was -12.8 +/- 1.9 mV (n = 4) in the absence of drug, -16.4 +/- 2.5 mV (n = 4) in 1 microM (+)202,791, and -31.4 +/- 0.4 mV (n = 4) in 1 microM (-)202,791. The rate of onset of action of the agonist and antagonist enantiomers of BAY K 8644 and Sandoz 202,791 was studied by rapid application during 20-ms depolarizing steps from different holding potentials to +30 mV at 1 or 0.2 Hz. The drugs were applied as concentration jumps between two single pulses of a pulse train. The rates of onset of drug action on peak IBa during a 1-Hz pulse train were concentration dependent over the range of 100 nM-3 microM for both (+) and (-)202,791. The rate of onset of inhibition of peak current by antagonist enantiomers was not significantly influenced by the test pulse frequency. At a holding potential of -60 mV, the onset rate of the increase in peak IBa on application of 1 microM of agonist enantiomers (+)202,791 or (-)BAY K 8644 during a train of pulses occurred with mean time constants of 2.1 +/- 0.7 s (n = 7) and 2.3 +/- 0.2 s (n = 4), respectively. The onset of current increase on application of 1 microM (+)202,791 during a single voltage clamp step to 20 mV was faster, with a mean time constant of 380 +/- 80 ms (n = 3).

scholarly journals Muscarinic activation of transient inward current and contraction in canine colon circular smooth muscle cells

2001 ◽  
Vol 79 (1) ◽  
pp. 34-42
Author(s):  
A Molleman ◽  
L WC Liu ◽  
J D Huizinga
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscarinic Receptor ◽  
Outward Current ◽  
Cyclopiazonic Acid ◽  
Muscle Cells ◽  
Transient Outward Current ◽  
Inward Current ◽  
Circular Smooth Muscle ◽  
Transient Inward Current

Muscarinic receptor mediated membrane currents and contractions were studied in isolated canine colon circular smooth muscle cells. Carbachol (10–5M) evoked a slow transient inward current that was superimposed by a transient outward current at holding potentials greater than –50 mV. Carbachol contracted the cells by 70 ± 2%. The effects of carbachol were blocked by atropine (10–6M), tetraethyl ammonium (20 mM), and BAPTA-AM (25 mM applied for 20 min). The inward current and contraction were not sensitive to diltiazem (10–5M), nitrendipine (3 × 10–7M), niflumic acid (10–5M), or N-phenylanthranilic acid (10–4M), but were gradually inhibited after repetitive stimulations in Ca2+free solution. Ni2+(2 mM) inhibited the inward current by 67 ± 4%. The inward current reversed at +15 mV. The outward component could be selectively inhibited by iberiotoxin (20 nM) or by intracellular Cs+. Repeated stimulation in the presence of cyclopiazonic acid (CPA, 3 µM) inhibited the carbachol-induced outward current and partially inhibited contraction. CPA did not inhibit the inward current. In conclusion, muscarinic receptor stimulation evoked a CPA-sensitive calcium release that caused contraction and a CPA-insensitive transient inward current was activated that is primarily carried by Ca2+ions and is sensitive to Ni2+.Key words: calcium, carbachol, smooth muscle, cyclopiazonic acid, sarcoplasmic reticulum.

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