Ca2+ coupling in vascular smooth muscle: Mg2+ and buffer effects on contractility and membrane Ca2+ movements

1982 ◽  
Vol 60 (4) ◽  
pp. 459-482 ◽  
Author(s):  
B. M. Altura ◽  
B. T. Altura ◽  
A. Carella ◽  
P. D. M. V. Turlapaty
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Reactivity ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Vascular Smooth Muscles ◽  
Disease States ◽  
Naturally Occurring ◽  
Ca Uptake ◽  
Coupling Processes

An examination of the literature, over the past two decades, reveals that (1) in studies of different types of vascular smooth muscles, Mg2+ is often either left out of physiological salt solutions or reduced in concentration compared with that in blood; and (2) when excitation–contraction coupling processes have been examined in isolated vascular tissues and cells, a number of artificial (synthetic) amine and organic zwitterion buffers have often been substituted for the naturally occurring bicarbonate and phosphate anions found in the blood and in cells. The influence of extracellular magnesium ions ([Mg2+]o) on tone, contractility, reactivity, and divalent cation movements in vascular smooth muscles, and how they may relate to certain vascular disease states, is reviewed. Data are presented and reviewed which indicate that many of the most commonly used artificial buffers (e.g., Tris. HEPES, MOPS, Bicine, PIPES, imidazole) can exert adverse effects on contractility and reactivity of certain arterial and venous smooth muscles. The data reviewed herein suggest that [Mg2+]o and membrane Mg are important in the regulation of vascular tone, vascular reactivity, and in control of Ca uptake, content, and distribution in smooth muscle cells. [Formula: see text] and (or) PO42−anions may be important for normal maintenance of excitability and reactivity and in the control of Ca uptake, content, and distribution in smooth muscle cells.

Characterization of [3H]nifedipine binding to intact vascular smooth muscle cells

1988 ◽  
Vol 254 (1) ◽  
pp. C45-C52 ◽  
Author(s):  
K. Sumimoto ◽  
M. Hirata ◽  
H. Kuriyama
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Binding Capacity ◽  
Specific Binding ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Scatchard Analysis ◽  
Intact Cells ◽  
Porcine Coronary Artery ◽  
Control Value

Specific binding of the dihydropyridine Ca2+ antagonist [3H]nifedipine to dispersed smooth muscle cells of the porcine coronary artery was investigated and the findings were compared with the binding to microsomes of smooth muscles. Specific binding to intact cells was saturable and reversible. The dissociation constant was 1.93 +/- 0.42 nM and the maximal binding capacity was 59.6 +/- 12.4 fmol/10(6) cells, as assessed by Scatchard analysis of the equilibrium binding at 25 degrees C. The Kd value with intact cells was slightly higher than that observed with microsomes. Specific binding of [3H]nifedipine to intact cells was completely displaced by unlabeled dihydropyridine derivatives. Among other Ca2+ antagonists, verapamil and d-cis-diltiazem partially and flunarizine completely inhibited the binding. In the case of microsomes, d-cis-diltiazem stimulated the binding of [3H]nifedipine. These results suggest that there may be multiple binding sites for different subclasses of Ca2+ antagonists. Polyvalent cations had no effect on the binding to intact cells. In the case of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA)-treated microsomes, the addition of CaCl2 and BaCl2 increased the Bmax, but the Kd value remained unchanged. MnCl2 and CdCl2 had stimulatory or inhibitory effects, depending on the concentrations, whereas LaCl3 had no effect. The effect of membrane depolarization on the binding was also examined. When the intact cells were incubated in high [K+]o solution for 60 min, the Kd was lowered to 1.4 nM from the control value of 2.0 nM, thereby indicating that [3H]nifedipine binds to Ca2+ channels, with a higher affinity, at depolarized states.

Molecular diversity of KVα- and β-subunit expression in canine gastrointestinal smooth muscles

1999 ◽  
Vol 277 (1) ◽  
pp. G127-G136 ◽  
Author(s):  
Anne Epperson ◽  
Helena P. Bonner ◽  
Sean M. Ward ◽  
William J. Hatton ◽  
Karri K. Bradley ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Pcr Analysis ◽  
Transcriptional Level ◽  
Gi Tract ◽  
Excitable Cells ◽  
Subunit Expression ◽  
Molecular Components

Voltage-activated K+(KV) channels play an important role in regulating the membrane potential in excitable cells. In gastrointestinal (GI) smooth muscles, these channels are particularly important in modulating spontaneous electrical activities. The purpose of this study was to identify the molecular components that may be responsible for the KV currents found in the canine GI tract. In this report, we have examined the qualitative expression of eighteen different KV channel genes in canine GI smooth muscle cells at the transcriptional level using RT-PCR analysis. Our results demonstrate the expression of KV1.4, KV1.5, KV1.6, KV2.2, and KV4.3 transcripts in all regions of the GI tract examined. Transcripts encoding KV1.2, KVβ1.1, and KVβ1.2 subunits were differentially expressed. KV1.1, KV1.3, KV2.1, KV3.1, KV3.2, KV3.4, KV4.1, KV4.2, and KVβ2.1 transcripts were not detected in any GI smooth muscle cells. We have also determined the protein expression for a subset of these KV channel subunits using specific antibodies by immunoblotting and immunohistochemistry. Immunoblotting and immunohistochemistry demonstrated that KV1.2, KV1.4, KV1.5, and KV2.2 are expressed at the protein level in GI tissues and smooth muscle cells. KV2.1 was not detected in any regions of the GI tract examined. These results suggest that the wide array of electrical activity found in different regions of the canine GI tract may be due in part to the differential expression of KV channel subunits.

Effects of prostaglandin F2α on membrane currents in rabbit middle cerebral arterial smooth muscle cells

2003 ◽  
Vol 284 (3) ◽  
pp. H1018-H1027 ◽  
Author(s):  
Nari Kim ◽  
Jin Han ◽  
Euiyong Kim
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Membrane Potentials ◽  
Delayed Rectifier ◽  
Direct Effects ◽  
Patch Clamp Technique ◽  
Arterial Smooth Muscle ◽  
Arterial Smooth Muscle Cells

Although PGF2αaffects contractility of vascular smooth muscles, no studies to date have addressed the electrophysiological mechanism of this effect. The purpose of our investigation was to examine the direct effects of PGF2α on membrane potentials, Ca2+-activated K+ (KCa) channels, delayed rectifier K+ (KV) channels, and L-type Ca2+channels with the patch-clamp technique in single rabbit middle cerebral arterial smooth muscle cells (SMCs). PGF2αsignificantly hyperpolarized membrane potentials and increased the amplitudes of total K+ currents. PGF2αincreased open-state probability but had little effect on the open and closed kinetics of KCa channels. PGF2αincreased the amplitudes of KV currents with a leftward shift of the activation and inactivation curves and a decrease in the activation time constant. PGF2α decreased the amplitudes of L-type Ca2+ currents without any significant change in threshold or apparent reversal potentials. This study provides the first finding that the direct effects of PGF2α on middle cerebral arterial SMCs, at least in part, could attenuate vasoconstriction.

scholarly journals Interstitial Cells: Regulators of Smooth Muscle Function

2014 ◽  
Vol 94 (3) ◽  
pp. 859-907 ◽  
Author(s):  
Kenton M. Sanders ◽  
Sean M. Ward ◽  
Sang Don Koh
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Motor Neurons ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Interstitial Cells ◽  
Pacemaker Activity ◽  
Molecular Features ◽  
Molecular Phenotypes ◽  
Cells Of Cajal

Smooth muscles are complex tissues containing a variety of cells in addition to muscle cells. Interstitial cells of mesenchymal origin interact with and form electrical connectivity with smooth muscle cells in many organs, and these cells provide important regulatory functions. For example, in the gastrointestinal tract, interstitial cells of Cajal (ICC) and PDGFRα+cells have been described, in detail, and represent distinct classes of cells with unique ultrastructure, molecular phenotypes, and functions. Smooth muscle cells are electrically coupled to ICC and PDGFRα+cells, forming an integrated unit called the SIP syncytium. SIP cells express a variety of receptors and ion channels, and conductance changes in any type of SIP cell affect the excitability and responses of the syncytium. SIP cells are known to provide pacemaker activity, propagation pathways for slow waves, transduction of inputs from motor neurons, and mechanosensitivity. Loss of interstitial cells has been associated with motor disorders of the gut. Interstitial cells are also found in a variety of other smooth muscles; however, in most cases, the physiological and pathophysiological roles for these cells have not been clearly defined. This review describes structural, functional, and molecular features of interstitial cells and discusses their contributions in determining the behaviors of smooth muscle tissues.

A survey of the new findings presented and the discussions arising during sessions I, II and lII

1973 ◽  
Vol 265 (867) ◽  
pp. 157-165 ◽  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Muscle Physiology ◽  
Muscle Fibres ◽  
New Findings ◽  
Separate Identity ◽  
Skeletal Muscle Fibres ◽  
Passive Electrical Properties

One of the earliest studies on the physiology of smooth muscle was that reported by Engelmann over 100 years ago. In setting the stage for this discussion on new developments in smooth muscle physiology, Professor Bozler recalled Engelmann’s description of the ureter as a ‘giant hollow muscle fibre’. Recent work on the passive electrical properties of smooth muscle has shown that Engelmann’s concept of the syncytial behaviour of smooth muscle is true for a great many smooth muscles - perhaps for all vertebrate smooth muscles. When smooth muscle cells come into contact they interact with each other so as to form a tissue. In this sense, a community of smooth muscle cells is analogous with the liver, epithelial tissues and the heart. One can contrast this ‘collective’ behaviour of smooth muscle cells with the separate identity maintained by most nerve cells and skeletal muscle fibres.

scholarly journals Assembly of Smooth Muscle Myosin by the 38k Protein, a Homologue of a Subunit of Pre-mRNA Splicing Factor-2

2000 ◽  
Vol 148 (4) ◽  
pp. 653-664 ◽  
Author(s):  
Tsuyoshi Okagaki ◽  
Akio Nakamura ◽  
Tomohiko Suzuki ◽  
Kazuhiro Ohmi ◽  
Kazuhiro Kohama
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Smooth Muscle Myosin ◽  
Mrna Splicing ◽  
Splicing Factor ◽  
A Subunit ◽  
Myosin Binding ◽  
Muscle Myosin

Smooth muscle myosin in the dephosphorylated state does not form filaments in vitro. However, thick filaments, which are composed of myosin and myosin-binding protein(s), persist in smooth muscle cells, even if myosin is subjected to the phosphorylation– dephosphorylation cycle. The characterization of telokin as a myosin-assembling protein successfully explained the discrepancy. However, smooth muscle cells that are devoid of telokin have been observed. We expected to find another ubiquitous protein with a similar role, and attempted to purify it from chicken gizzard. The 38k protein bound to both phosphorylated and dephosphorylated myosin to a similar extent. The effect of the myosin-binding activity was to assemble dephosphorylated myosin into filaments, although it had no effect on the phosphorylated myosin. The 38k protein bound to myosin with both COOH-terminal 20 and NH2-terminal 28 residues of the 38k protein being essential for myosin binding. The amino acid sequence of the 38k protein was not homologous to telokin, but to human p32, which was originally found in nuclei as a subunit of pre-mRNA splicing factor-2. Western blotting showed that the protein was expressed in various smooth muscles. Immunofluorescence microscopy with cultured smooth muscle cells revealed colocalization of the 38k protein with myosin and with other cytoskeletal elements. The absence of nuclear immunostaining was discussed in relation to smooth muscle differentiation.

scholarly journals Depolarization-Stimulated Contractility of Gastrointestinal Smooth Muscle in Calcium-Free Solution: A Review

2011 ◽  
Vol 2011 ◽  
pp. 1-3 ◽  
Author(s):  
Emily D. Evans ◽  
Allen W. Mangel
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Smooth Muscle Cells ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Threshold Level ◽  
Slow Waves ◽  
Free Solution ◽  
Gastrointestinal Smooth Muscle ◽  
Small Muscle

The membrane of most gastrointestinal smooth muscles shows slow waves, slow rhythmic changes in membrane potential. Slow waves serve to bring the membrane potential of smooth muscle cells to a threshold level that elicits a second electrical event known as the spike or action potential. The inward current of the spike, in most gastrointestinal smooth muscle preparations, is carried, at least in part, by calcium. Indeed, considering the narrow diameter of smooth muscle cells, some have hypothesized that the influx of calcium during the spike is sufficient for activation of the contractile machinery. Findings consistent with this include marked reduction in contractility during exposure of muscle segments to blockers of L-type calcium channels or following reductions in external calcium levels. However, it has also been observed that following exposure of muscle segments to external bathing solutions containing no added calcium plus 5 mM EGTA to remove any remaining extracellular calcium, contractions can be triggered following membrane depolarization. It is noteworthy that in isolated smooth muscle cells or in small muscle segments, during incubation in calcium-free solution, depolarization does not induce contractions. The present paper discusses the evidence in support of depolarization-mediated contractions occurring in gastrointestinal smooth muscle segments during incubation in solutions devoid of calcium.

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