scholarly journals Magnesium induced vascular relaxation and role of Calcium-dependent K+ Channels

2013 ◽  
Vol 1 (1) ◽  
pp. 9-13
Author(s):  
K Upadhyay-Dhungel ◽  
CJ Kim ◽  
A Dhungel
Keyword(s):  
Smooth Muscle ◽  
Patch Clamp ◽  
Smooth Muscle Cells ◽  
Channel Blocker ◽  
Muscle Cells ◽  
K Channel ◽  
Vascular Relaxation ◽  
Patch Clamp Technique ◽  
Calcium Dependent ◽  
K Currents

Background and objectives: Magnesium is established as a neuro-protective agent and now also known as a vasodilator. It has been known for treating vasospasm following subarachnoid hemorrhage. However, its action mechanism in cerebral vascular relaxation is not clear. Potassium channels play a pivotal role in the relaxation of smooth muscle cells. To investigate their role in magnesium-induced relaxation of basilar smooth muscle cells, we examined the effect of magnesium on potassium channels using the patch clamp technique on cells from rabbit basilar artery. Material and Methods: Fresh smooth muscle cells were isolated from the basilar artery by enzyme treatment. Whole cell current recording was done using patch-clamp technique. Appropriate bath solution was used to have potassium current. The effect of Magnesium was observed and to identify the potassium (K+) channel involved in the magnesium-induced currents, different potassium channel blockers were used. Results: Magnesium increased the step pulse-induced outward K+ currents by more than fortyfive percent over control level (p<0.01). The outward K+ current was decreased significantly by application of tetraethylammonium, a non-specific K+ channel blocker, and by iberiotoxin, a largeconductance Ca2+-activated K+ (BKCa) channel blocker, but was not inhibited by glibenclamide an ATP-sensitive K+ (KATP) channel blocker. Magnesium failed to increase the outward K+ currents in the presence of IBX. Conclusion: These results demonstrate that calcium dependent pottassium (BKCa) channels has role in magnesium induced vascular relaxation in rabbit basilar smooth muscle cells and needs to be worked out for human. DOI: http://dx.doi.org/10.3126/jmcjms.v1i1.7880 Janaki Medical College Journal of Medical Sciences (2013) Vol. 1 (1):9-13

Pharmacology of ATP-sensitive K+ currents in smooth muscle cells from rabbit mesenteric artery

1995 ◽  
Vol 269 (5) ◽  
pp. C1112-C1118 ◽  
Author(s):  
J. M. Quayle ◽  
A. D. Bonev ◽  
J. E. Brayden ◽  
M. T. Nelson
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Mesenteric Artery ◽  
Katp Channels ◽  
Muscle Cells ◽  
K Channel ◽  
Patch Clamp Technique ◽  
Functional Studies ◽  
Rabbit Mesenteric Artery ◽  
K Currents

The inference that ATP-sensitive K+ (KATP) channels are involved in arterial responses to the synthetic K+ channel openers, hypoxia, adenosine, and calcitonin gene-related peptide, has relied on the sensitivity of these responses to the sulfonylureas glibenclamide and tolbutamide and to tetraethylammonium (TEA+). The inhibition of KATP currents by glibenclamide, tolbutamide, and TEA+ was investigated in single smooth muscle cells from rabbit mesenteric artery by use of the whole cell patch-clamp technique. The synthetic K+ channel openers pinacidil (half-activation 0.6 microM), cromakalim (half-activation 1.9 microM), and diazoxide (half-activation 37.1 microM) activated K(+)-selective currents that were blocked by glibenclamide. Elevation of pipette (intracellular) ATP concentration decreased K+ currents induced by pinacidil. Half-inhibition of KATP currents by glibenclamide and tolbutamide occurred at 101 nM and 351 microM, respectively. KATP currents were also inhibited by external TEA+, with half-inhibition at 6.2 mM. The results indicate that glibenclamide is an effective inhibitor of KATP channels in arterial smooth muscle and that tolbutamide and TEA+ are much less effective. Furthermore, these results support numerous functional studies that have demonstrated that the vasorelaxations to K+ channel openers are inhibited by < 10 microM glibenclamide but not by < 1 mM TEA+.

Ketamine blocks Ca2+-activated K+ channels in rabbit cerebral arterial smooth muscle cells

2003 ◽  
Vol 285 (3) ◽  
pp. H1347-H1355 ◽  
Author(s):  
Jin Han ◽  
Nari Kim ◽  
Hyun Joo ◽  
Euiyong Kim
Keyword(s):  
Smooth Muscle ◽  
Patch Clamp ◽  
Smooth Muscle Cells ◽  
Cerebral Arteries ◽  
Muscle Cells ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Arterial Smooth Muscle ◽  
Clamp Technique ◽  
Arterial Smooth Muscle Cells

Although ketamine and Ca2+-activated K+ (KCa) channels have been implicated in the contractile activity regulation of cerebral arteries, no studies have addressed the specific interactions between ketamine and the KCa channels in cerebral arteries. The purpose of this study was to examine the direct effects of ketamine on KCa channel activities using the patch-clamp technique in single-cell preparations of rabbit middle cerebral arterial smooth muscle. We tested the hypothesis that ketamine modulates the KCa channel activity of the cerebral arterial smooth muscle cells of the rabbit. Vascular myocytes were isolated from rabbit middle cerebral arteries using enzymatic dissociation. Single KCa channel activities of smooth muscle cells from rabbit cerebral arteries were recorded using the patch-clamp technique. In the inside-out patches, ketamine in the micromolar range inhibited channel activity with a half-maximal inhibition of the ketamine conentration value of 83.8 ± 12.9 μM. The Hill coefficient was 1.2 ± 0.3. The slope conductance of the current-voltage relationship was 320.1 ± 2.0 pS between 0 and +60 mV in the presence of ketamine and symmetrical 145 mM K+. Ketamine had little effect on either the voltage-dependency or open- and closed-time histograms of KCa channel. The present study clearly demonstrates that ketamine inhibits KCa channel activities in rabbit middle cerebral arterial smooth muscle cells. This inhibition of KCa channels may represent a mechanism for ketamine-induced cerebral vasoconstriction.

Effects of the gap junction blocker glycyrrhetinic acid on gastrointestinal smooth muscle cells

2005 ◽  
Vol 288 (4) ◽  
pp. G832-G841 ◽  
Author(s):  
Yukari Takeda ◽  
Sean M. Ward ◽  
Kenton M. Sanders ◽  
Sang Don Koh
Keyword(s):  
Smooth Muscle ◽  
Patch Clamp ◽  
Smooth Muscle Cells ◽  
Gap Junctions ◽  
Lucifer Yellow ◽  
Muscle Cells ◽  
Glycyrrhetinic Acid ◽  
Delayed Rectifier ◽  
Dependent Manner ◽  
Patch Clamp Technique

In the tunica muscularis of the gastrointestinal (GI) tract, gap junctions form low-resistance pathways between pacemaker cells known as interstitial cells of Cajal (ICCs) and between ICC and smooth muscle cells. Coupling via these junctions facilitates electrical slow-wave propagation and responses of smooth muscle to enteric motor nerves. Glycyrrhetinic acid (GA) has been shown to uncouple gap junctions, but previous studies have shown apparent nonspecific effects of GA in a variety of tissues. We tested the effects of GA using isometric force measurements, intracellular microelectrode recordings, the patch-clamp technique, and the spread of Lucifer yellow within cultured ICC networks. In murine small intestinal muscles, β-GA (10 μM) decreased phasic contractions and depolarized resting membrane potential. Preincubation of GA inhibited the spread of Lucifer yellow, increased input resistance, and decreased cell capacitance in ICC networks, suggesting that GA uncoupled ICCs. In patch-clamp experiments of isolated jejunal myocytes, GA significantly decreased L-type Ca2+ current in a dose-dependent manner without affecting the voltage dependence of this current. The IC50 for Ca2+ currents was 1.9 μM, which is lower than the concentrations used to block gap junctions. GA also significantly increased large-conductance Ca2+-activated K+ currents but decreased net delayed rectifier K+ currents, including 4-aminopyridine and tetraethylammonium-resistant currents. In conclusion, the reduction of phasic contractile activity of GI muscles by GA is likely a consequence of its inhibitory effects on gap junctions and voltage-dependent Ca2+ currents. Membrane depolarization may be a consequence of uncoupling effects of GA on gap junctions between ICCs and smooth muscles and inhibition of K+ conductances in smooth muscle cells.

Ca-activated K channel in cultured smooth muscle cells of rat aortic media

1988 ◽  
Vol 255 (3) ◽  
pp. H410-H418 ◽  
Author(s):  
J. Sadoshima ◽  
N. Akaike ◽  
H. Tomoike ◽  
H. Kanaide ◽  
M. Nakamura
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Rat Aorta ◽  
K Channel ◽  
Patch Clamp Technique ◽  
Intracellular Ca ◽  
Aortic Media ◽  
Cultured Smooth Muscle Cells ◽  
Low Sensitivity

Electrical and pharmacological properties of the single Ca-activated K channel in cultured smooth muscle cells (SMC) of the rat aorta were studied with the patch-clamp technique. The Ca-activated K channel had a slope conductance (gamma K) of 135 +/- 2 pS (mean +/- SE; n = 5) in symmetrical 142 mM K solutions. The reversal potentials show a 56-mV change for a 10-fold change in the external K concentration. Probability of the channel opening increased when the intracellular Ca concentration ([Ca]i) was increased over 10(-7) M or the membrane was depolarized. The channel was blocked by either external tetraethylammonium (TEA, 10–30 mM) or by internal Ba (1–5 mM). Channel activities were characterized by burst-like openings. Open-time histogram was fitted with a single exponential (tau = 1.3 ms at +10 mV and 10(-7) M [Ca]i), whereas the closed-time histogram was fitted with two exponentials (tau 1 = 0.7 ms and tau 2 = 111 ms). The permeability ratio for monovalent cations calculated with the Goldman-Hodgkin-Katz equation was K:Rb:Na = 1:0.7: less than 0.01. We conclude from these observations that the Ca-activated K channel in cultured SMC of the rat aorta is characterized by a middle size gamma K, activation by [Ca]i increase and depolarization, relatively low sensitivity to TEA, and high selectivity for K ions.

Cyclic AMP modulates Ca-activated K channel in cultured smooth muscle cells of rat aortas

1988 ◽  
Vol 255 (4) ◽  
pp. H754-H759 ◽  
Author(s):  
J. Sadoshima ◽  
N. Akaike ◽  
H. Kanaide ◽  
M. Nakamura
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Rat Aorta ◽  
K Channel ◽  
Free Calcium ◽  
Bathing Solution ◽  
Patch Clamp Technique ◽  
K Channels ◽  
Cultured Smooth Muscle Cells

Effects of adenosine 3',5'-cyclic monophosphate (cAMP) on single Ca-activated K current (IK(Ca)) in cultured smooth muscle cells of the rat aorta were investigated with the patch-clamp technique. In cell-attached patch configurations, extracellular application of isoproterenol (10(-5) M) increased the Ca-activated K currents. The increase in the currents was due to an increase in the probability of channel openings (Po). Neither unit conductance nor the maximum number of the channel in the patch was affected by the drug. The effects were inhibited by adding propranolol (10(-6) M). The extracellular application of forskolin (10(-5) M) or dibutyryl cAMP (10(-4) M) mimicked the effects of isoproterenol. In inside-out patch configurations, activated cAMP-dependent protein kinase (A kinase) in the bathing solution increased the sensitivity of the Ca-activated K channels to intracellular free calcium concentration ([Ca]i) and enhanced Po. Kinetic analyses of the IK(Ca) showed that cAMP-dependent phosphorylation of the Ca-activated K channels significantly reduced the mean closed time between bursting openings. We conclude from these observations that the Ca-activated K channels in aortic cells may increase Po through cAMP-dependent phosphorylation.

Relaxant effect of xenin on rat ileum is mediated by apamin-sensitive neurotensin-type receptors

1997 ◽  
Vol 272 (1) ◽  
pp. G190-G196 ◽  
Author(s):  
A. Clemens ◽  
S. Katsoulis ◽  
R. Nustede ◽  
J. Seebeck ◽  
K. Seyfarth ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Channel Blocker ◽  
Muscle Cells ◽  
K Channel ◽  
Binding Studies ◽  
Relaxant Effect ◽  
Structure Activity ◽  
Neuromedin N

The action of xenin, a novel 25-residue peptide of the neurotensin (NT)/xenopsin family, was investigated in isolated rat ileal muscle strips and in dispersed longitudinal smooth muscle cells of rat small intestine in vitro. Xenin relaxes KCl-precontracted ileal strips dose dependently (1 nM-3 microM). The order of potency of the investigated peptides was as follows: xenopsin = NT = xenin > neuromedin N. Kinetensin was inactive. Tetrodotoxin, hexamethonium, tetraethylammonium, 4-aminopyridine, and NG-nitro-L-arginine did not influence the relaxant effects of xenin or NT, whereas the K+ channel blocker apamin nearly abolished their effects. Desensitization against one of the peptides or blockade of NT receptors by SR-48692 prevented the effect of xenin and NT. Structure-activity experiments revealed that the COOH-terminal part of the molecules of xenin and NT is essential for biological activity. Experiments with isolated dispersed smooth muscle cells and binding studies on intestinal smooth muscle cell membranes confirmed and extended the results obtained with muscle strips. In conclusion, xenin relaxes rat ileal smooth muscle via a muscular NT-type apamin-sensitive receptor.

scholarly journals Vasodilatory Effect of Phellinus linteus Extract in Rat Mesenteric Arteries

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3160
Author(s):  
Youngin Kwon ◽  
Chae Eun Haam ◽  
Seonhee Byeon ◽  
Soo Jung Choi ◽  
Dong-Hoon Shin ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Channel Blocker ◽  
Muscle Cells ◽  
Mesenteric Arteries ◽  
K Channel ◽  
Phellinus Linteus ◽  
Ikca Channel

Phellinus linteus is a well-known medicinal mushroom that is widely used in Asian countries. In several experimental models, Phellinus linteus extracts were reported to have various biological effects, including anti-inflammatory, anti-cancer, hepatoprotective, anti-diabetic, neuroprotective, and anti-angiogenic activity. In the present study, several bioactive compounds, including palmitic acid ethyl ester and linoleic acid, were identified in Phellinus linteus. The intermediate-conductance calcium-activated potassium channel (IKCa) plays an important role in the regulation of the vascular smooth muscle cells’ (VSMCs) contraction and relaxation. The activation of the IKCa channel causes the hyperpolarization and relaxation of VSMCs. To examine whether Phellinus linteus extract causes vasodilation in the mesenteric arteries of rats, we measured the isometric tension using a wire myograph. After the arteries were pre-contracted with U46619 (a thromboxane analogue, 1 µM), Phellinus linteus extract was administered. The Phellinus linteus extract induced vasodilation in a dose-dependent manner, which was independent of the endothelium. To further investigate the mechanism, we used the non-selective K+ channel blocker tetraethylammonium (TEA). TEA significantly abolished Phellinus linteus extract-induced vasodilation. Thus, we tested three different types of K+ channel blockers: iberiotoxin (BKca channel blocker), apamin (SKca channel blocker), and charybdotoxin (IKca channel blocker). Charybdotoxin significantly inhibited Phellinus linteus extract-induced relaxation, while there was no effect from apamin and iberiotoxin. Membrane potential was measured using the voltage-sensitive dye bis-(1,3-dibutylbarbituric acid)-trimethine oxonol (DiBAC4(3)) in the primary isolated vascular smooth muscle cells (VSMCs). We found that the Phellinus linteus extract induced hyperpolarization of VSMCs, which is associated with a reduced phosphorylation level of 20 KDa myosin light chain (MLC20).

Sign in / Sign up

Export Citation Format

Share Document