scholarly journals Voltage-dependent inward currents in smooth muscle cells of skeletal muscle arterioles

2017 ◽  
Author(s):  
Alexandra V. Ulyanova ◽  
Roman E. Shirokov
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Action Potentials ◽  
Channel Blocker ◽  
Muscle Cells ◽  
Maximal Velocity ◽  
Voltage Gated ◽  
Voltage Dependent ◽  
Inward Currents

AbstractVoltage-dependent inward currents responsible for the depolarizing phase of action potentials were characterized in smooth muscle cells of 4th order arterioles in mouse skeletal muscle. Currents through L-type Ca2+ channels were expected to be dominant; however, action potentials were not eliminated in nominally Ca2+-free bathing solution or by addition of L-type Ca2+ channel blocker nifedipine (10 μM). Instead, Na+ channel blocker tetrodotoxin (TTX, 1 μM) reduced the maximal velocity of the upstroke at low, but not at normal (2 mM), Ca2+ in the bath. The magnitude of TTX-sensitive currents recorded with 140 mM Na+ was about 20 pA/pF. TTX-sensitive currents decreased five-fold when Ca2+ increased from 2 to 10 mM. The currents reduced three-fold in the presence of 10 mM caffeine, but remained unaltered by 1 mM of isobutylmethylxanthine (IBMX). In addition to L-type Ca2+ currents (15 pA/pF in 20 mM Ca2+), we also found Ca2+ currents that are resistant to 10 μM nifedipine (5 pA/pF in 20 mM Ca2+). Based on their biophysical properties, these Ca2+ currents are likely to be through voltage-gated T-type Ca2+ channels. Our results suggest that Na+ and at least two types (T- and L-) of Ca2+ voltage-gated channels contribute to depolarization of smooth muscle cells in skeletal muscle arterioles. Voltage-gated Na+ channels appear to be under a tight control by Ca2+ signaling.

scholarly journals Functional characterization of voltage-dependent Ca2+ channels in mouse pulmonary arterial smooth muscle cells: divergent effect of ROS

2013 ◽  
Vol 304 (11) ◽  
pp. C1042-C1052 ◽  
Author(s):  
Eun A. Ko ◽  
Jun Wan ◽  
Aya Yamamura ◽  
Adriana M. Zimnicka ◽  
Hisao Yamamura ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Function ◽  
Electromechanical Coupling ◽  
Functional Characterization ◽  
Muscle Cells ◽  
Pulmonary Vascular Disease ◽  
High K ◽  
Voltage Dependent ◽  
Inward Currents

Electromechanical coupling via membrane depolarization-mediated activation of voltage-dependent Ca2+ channels (VDCC) is an important mechanism in regulating pulmonary vascular tone, while mouse is an animal model often used to study pathogenic mechanisms of pulmonary vascular disease. The function of VDCC in mouse pulmonary artery (PA) smooth muscle cells (PASMC), however, has not been characterized, and their functional role in reactive oxygen species (ROS)-mediated regulation of vascular function remains unclear. In this study, we characterized the electrophysiological and pharmacological properties of VDCC in PASMC and the divergent effects of ROS produced by xanthine oxidase (XO) and hypoxanthine (HX) on VDCC in PA and mesenteric artery (MA). Our data show that removal of extracellular Ca2+ or application of nifedipine, a dihydropyridine VDCC blocker, both significantly inhibited 80 mM K+-mediated PA contraction. In freshly dissociated PASMC, the maximum inward Ca2+ currents were −2.6 ± 0.2 pA/pF at +10 mV (with a holding potential of −70 mV). Window currents were between −40 and +10 mV with a peak at −15.4 mV. Nifedipine inhibited currents with an IC50 of 0.023 μM, and 1 μM Bay K8644, a dihydropyridine VDCC agonist, increased the inward currents by 61%. XO/HX attenuated 60 mM K+-mediated increase in cytosolic free Ca2+ concentration ([Ca2+]cyt) due to Ca2+ influx through VDCC in PASMC. Exposure to XO/HX caused relaxation in PA preconstricted by 80 mM K+ but not in aorta and MA. In contrast, H2O2 inhibited high K+-mediated increase in [Ca2+]cyt and caused relaxation in both PA and MA. Indeed, RT-PCR and Western blot analysis revealed significantly lower expression of CaV1.3 in MA compared with PA. Thus our study characterized the properties of VDCC and demonstrates that ROS differentially regulate vascular contraction by regulating VDCC in PA and systemic arteries.

scholarly journals Hypercholesterolemia abolishes voltage-dependent K+ channel contribution to adenosine-mediated relaxation in porcine coronary arterioles

2005 ◽  
Vol 288 (2) ◽  
pp. H568-H576 ◽  
Author(s):  
C. L. Heaps ◽  
D. L. Tharp ◽  
D. K. Bowles
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Channel Blocker ◽  
Muscle Cells ◽  
Left Ventricular ◽  
Apical Region ◽  
Luminal Diameter ◽  
Flow Reserve ◽  
Voltage Dependent ◽  
Coronary Arterioles

Hypercholesterolemic patients display reduced coronary flow reserve in response to adenosine infusion. We previously reported that voltage-dependent K+ (Kv) channels contribute to adenosine-mediated relaxation of coronary arterioles isolated from male miniature swine. For this study, we hypothesized that hypercholesterolemia attenuates Kv channel contribution to adenosine-induced vasodilatation. Pigs were randomly assigned to a control or high fat/high cholesterol diet for 20–24 wk, and then killed. After completion of the experimental treatment, arterioles (∼150 μm luminal diameter) were isolated from the left-ventricular free wall near the apical region of the heart, cannulated, and pressurized at 40 mmHg. Adenosine-mediated relaxation was significantly attenuated in both endothelium-intact and -denuded arterioles from hypercholesterolemic compared with control animals. The classic Kv channel blocker, 4-aminopyridine (1 mM), significantly attenuated adenosine-mediated relaxation in arterioles isolated from control but not hypercholesterolemic animals. Furthermore, the nonselective K+ channel blocker, tetraethylammonium (TEA; 1 mM) significantly attenuated adenosine-mediated relaxation in arterioles from control but not hypercholesterolemic animals. In additional experiments, coronary arteriolar smooth muscle cells were isolated, and whole cell K v currents were measured. Kv currents were significantly reduced (∼15%) in smooth muscle cells from hypercholesterolemic compared with control animals. Furthermore, Kv current sensitive to low concentrations of TEA was reduced (∼45%) in smooth muscle cells from hypercholesterolemic compared with control animals. Our data indicate that hypercholesterolemia abolishes Kv channel contribution to adenosine-mediated relaxation in coronary arterioles, which may be attributable to a reduced contribution of TEA-sensitive K v channels in smooth muscle of hypercholesterolemic animals.

Mechanisms of hemolysate-induced [Ca2+]i elevation in cerebral smooth muscle cells

1995 ◽  
Vol 269 (6) ◽  
pp. H1874-H1890 ◽  
Author(s):  
H. Zhang ◽  
B. Weir ◽  
L. S. Marton ◽  
R. L. Macdonald ◽  
V. Bindokas ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Channel Blocker ◽  
Cyclopiazonic Acid ◽  
Muscle Cells ◽  
Excitation Wavelength ◽  
Free Solution ◽  
Voltage Dependent ◽  
Cytochrome P 450 ◽  
Isolated Rat

The effects of hemolysate on free cytosolic [Ca2+] ([Ca2+]i) homeostasis were studied in freshly isolated rat basilar artery smooth muscle cells using fura 2 and dual excitation wavelength microfluorimetry. Hemolysate reversibly produced a transient [Ca2+]i peak followed by a slowly decaying plateau which was absent in Ca(2+)-free solution. This effect of hemolysate was attenuated by 1) the sarcoplasmic reticulum Ca2+ pump inhibitors thapsigargin and cyclopiazonic acid, 2) the Ca2+ release-blocking agents ryanodine and dantrolene, 3) the cytochrome P-450 inhibitor econazole, and 4) the inorganic Ca2+ channel blocker lanthanum but was not significantly attenuated by 1) the receptor-regulated Ca2+ channel blocker SKF-96365 or 2) the voltage-dependent Ca2+ channel blocker nimodipine. Fractionation of hemolysate using membranes with specific pore sizes (0.5, 1, and 12-14 kDa) indicated that a component(s) > 0.5 but < 1 kDa could produce a similar [Ca2+]i peak and plateau while fractions > 1 and > 12-14 kDa produced a small and slow [Ca2+]i rise without a significant peak. ATP, which was found in hemolysate, produced a [Ca2+]i response similar to that of hemolysate. P2-purinoceptor antagonists significantly attenuated the effect of ATP, hemolysate, and the fractions < 1 and < 12-14 kDa. We conclude that hemolysate elevates [Ca2+]i by both releasing Ca2+ from internal stores and triggering Ca2+ entry, possibly from a voltage-independent Ca2+ influx pathway, an effect apparently identical to that of ATP.

Multiple transcripts of Ca2+ channel α1-subunits and a novel spliced variant of the α1C-subunit in rat ductus arteriosus

2006 ◽  
Vol 290 (4) ◽  
pp. H1660-H1670 ◽  
Author(s):  
Utako Yokoyama ◽  
Susumu Minamisawa ◽  
Satomi Adachi-Akahane ◽  
Toru Akaike ◽  
Isao Naguro ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Channel Blocker ◽  
Thymidine Incorporation ◽  
Ductus Arteriosus ◽  
Muscle Cells ◽  
Wistar Rat ◽  
Multiple Transcripts ◽  
Voltage Dependent ◽  
Spliced Variant

Voltage-dependent Ca2+ channels (VDCCs), which consist of multiple subtypes, regulate vascular tone in developing arterial smooth muscle, including the ductus arteriosus (DA). First, we examined the expression of VDCC subunits in the Wistar rat DA during development. Among α1-subunits, α1C and α1G were the most predominant isoforms. Maternal administration of vitamin A significantly increased α1C- and α1G-transcripts. Second, we examined the effect of VDCC subunits on proliferation of DA smooth muscle cells. We found that 1 μM nitrendipine (an L-type Ca2+ channel blocker) and kurtoxin (a T-type Ca2+ channel blocker) significantly decreased [3H]thymidine incorporation and that 3 μM efonidipine (an L- and T-type Ca2+ channel blocker) further decreased [3H]thymidine incorporation, suggesting that L- and T-type Ca2+ channels are involved in smooth muscle cell proliferation in the DA. Third, we found that a novel alternatively spliced variant of the α1C-isoform was highly expressed in the neointimal cushion of the DA, where proliferating and migrating smooth muscle cells are abundant. The basic channel properties of the spliced variant did not differ from those of the conventional α1C-subunit. We conclude that multiple VDCC subunits were identified in the DA, and, in particular, α1C- and α1G-subunits were predominant in the DA. A novel spliced variant of the α1C-subunit gene may play a distinct role in neointimal cushion formation in the DA.

Ionic basis of the action potential of guinea pig gallbladder smooth muscle cells

1993 ◽  
Vol 265 (6) ◽  
pp. C1552-C1561 ◽  
Author(s):  
L. Zhang ◽  
A. D. Bonev ◽  
M. T. Nelson ◽  
G. M. Mawe
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Action Potential ◽  
Smooth Muscle Cells ◽  
Action Potentials ◽  
Outward Current ◽  
Muscle Cells ◽  
Tetraethylammonium Chloride ◽  
Voltage Dependent ◽  
Calcium Activated Potassium Channels

Smooth muscle cells in the intact guinea pig gallbladder had a resting membrane potential of about -45 mV and had spontaneous action potentials that consisted of a rapid depolarization, a transient repolarization, a plateau phase, and a complete repolarization. These action potentials lasted approximately 570 ms and occurred at a frequency of approximately 0.4 Hz. Action potentials were abolished by the dihydropyridine (DHP)-sensitive Ca2+ channel blocker nifedipine (1.0 microM) and were enhanced by the DHP-sensitive Ca2+ channel agonist BAY K 8644 (0.5 microM). The K+ channel blockers tetraethylammonium chloride (5.0 mM) and 4-aminopyridine (4-AP; 2.0 mM) prolonged the action potential, whereas charybdotoxin (100 nM), a blocker of calcium-activated potassium channels, had no effect. Whole cell currents were characterized in enzymatically isolated smooth muscle cells from the same preparation. 4-AP, a blocker of voltage-dependent K+ channels, suppressed 70% of the outward current at 0 mV. Charybdotoxin (100 nM) reduced an additional 15% of the current at 0 mV. Single calcium-activated potassium channels were identified. The potential for half-activation of these channels, at a cytosolic Ca2+ concentration of 100 nM, was 66.8 mV. A fivefold increase in cytosolic Ca2+ resulted in a shift of the activation curve by -53 mV. External tetraethylammonium chloride (200 microM) reduced the mean single channel current by 48% at 0 mV. The whole cell outward current was abolished by replacement of intracellular K+ for Cs+. Ca2+ currents were inhibited by nifedipine and were increased by BAY K 8644. We conclude that DHP-sensitive voltage-dependent Ca2+ channels are responsible for the depolarization of the action potentials and that the repolarization is due to primarily 4-AP-sensitive K+ current.

Cholinergic regulation of voltage-dependent Ca2+ channels in porcine tracheal smooth muscle cells

1995 ◽  
Vol 269 (6) ◽  
pp. L776-L782 ◽  
Author(s):  
M. Yamakage ◽  
C. A. Hirshman ◽  
T. L. Croxton
Keyword(s):  
Smooth Muscle ◽  
Charge Carrier ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Tracheal Smooth Muscle ◽  
Whole Cell ◽  
Cholinergic Regulation ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Ca2 Channels

To investigate cholinergic regulation of voltage-dependent Ca2+ channels (VDCs) in airway smooth muscle, we measured inward currents through VDCs in enzymatically dispersed porcine tracheal smooth muscle cells using conventional (10 mM Ca2+ as charge carrier) and nystatin-perforated (5 mM Ba2+ as charge carrier) whole cell patch clamp techniques. Carbachol (CCh) had significant and dose-dependent inhibitory effects on inward currents (12% with 10(-7) M and 42% with 10(-6) M) in perforated whole cell clamp experiments, but had no effect on currents in conventional whole cell experiments. CCh also shifted the steady-state inactivation curve to more negative potentials. Further experiments tested the hypothesis that CCh inhibits VDCs in part by the activation of protein kinase C (PKC). Phorbol 12,13-diacetate, an exogenous PKC activator, inhibited currents through VDCs. and calphostin C, a specific PKC inhibitor, antagonized the inhibitory effect of CCh. Furthermore, intracellular exposure to the activating PKC fragment 530-558, using a pipette perfusion technique, also inhibited currents through VDCs. We conclude that cholinergic receptor stimulation can inhibit inward Ca2+ currents through VDCs of porcine tracheal smooth muscle and that this effect may be mediated in part by activation of PKC.

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