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At least 757 records · Page 42Linked to original sources
PubMed2001

Supramaximal stimuli do not evoke a maximal contraction in urinary bladder smooth muscle fibers.

BACKGROUND: Smooth muscle fibers can be stimulated with an electrical field, high potassium or carbachol. We studied the effect of combined, supramaximal stimulation on the isometric force and the maximum shortening velocity of the pig urinary bladder. MATERIALS AND METHODS: After determining the dose response curve of each stimulation type, we stimulated 8 fibers with cumulative addition of supramaximal stimuli. RESULTS: The isometric force elicited with either potassium, carbachol or electrical field stimulation alone was the same for each stimulus. After addition of a second or third different supramaximal stimulus, the force further increased to a value that was on average 40% higher. CONCLUSIONS: Carbachol, high potassium or electrical field stimulation work through different stimulation pathways. Maximum stimulation with one of the stimuli does not result in a maximum isometric force development and maximum shortening velocity.

Animals↗
PubMed2006

Serum starvation and growth factor receptor expression in vascular smooth muscle cells.

BACKGROUND: Smooth muscle cell (SMC) proliferation in atherosclerosis is regulated through the interaction of growth factors like platelet-derived growth factor-BB (PDGF-BB) and insulin-like growth factor-1 (IGF-1) and their receptors (R). We hypothesized that serum starvation of SMCs may affect PDGFbeta-R and IGF-1-R expression and, consequently, the effect of their cognate ligands on SMC survival/proliferation. METHODS AND RESULTS: Serum starvation significantly increases PDGFbeta-R but not IGF-1-R mRNA and protein expression in SMCs. PDGF-BB stimulates cell survival but not proliferation in serum-starved SMCs of the synthetic phenotype, whereas SMCs of the contractile phenotype respond to PDGF-BB by a significant increase in proliferation. Immunohistochemical analysis of coronary atherosclerotic lesions reveals PDGFbeta-R expression in SMCs in the lamina fibromuscularis, but not in the media and in healthy parts of the arterial wall. No such differential expression was observed for IGF-1-R. CONCLUSIONS: Differential regulation of PDGFbeta-R and IGF-1-R expression by serum starvation might represent a mechanism for the control of SMC survival/proliferation in atherogenesis and restenosis. The distribution of PDGFbeta-Rs and IGF-1-Rs in atherosclerotic lesions may indicate an effect of serum starvation on SMCs in the arterial wall.

Becaplermin↗
PubMed1995

TGF-beta and endothelial cells inhibit VCAM-1 expression on human vascular smooth muscle cells.

Vascular smooth muscle cells (VSMCs) are normally devoid of the adhesion protein vascular cell adhesion molecule-1 (VCAM-1), which has, however, been observed on human VSMCs in atheroma. We now show that cultured human saphenous vein VSMCs express small amounts of VCAM-1 and that the cytokine tumor necrosis factor-alpha (TNF-alpha) induces, in a time- and dose-dependent fashion, a significant increase in its expression. Interleukin (IL)-4, IL-1, and to a lesser extent interferon gamma have similar effects. TNF-alpha-stimulated human VSMCs demonstrate increased binding of T lymphocytes that is totally VCAM-1 mediated. The cytokine transforming growth factor-beta (TGF-beta) at 2.0 ng/mL inhibited basal VCAM-1 expression by 84 +/- 8% and the induction by TNF-alpha by between 56 +/- 16% and 77 +/- 15% depending on the dose of TNF. Furthermore, coculture on opposing sides of a polycarbonate filter of human VSMCs with human umbilical vein endothelial cells also inhibited the induction of VCAM-1 by 47 +/- 6%. As active TGF-beta is produced upon the coculture of VSMCs and endothelial cells, we suggest that the close physical proximity of these cells in vivo is responsible for the lack of expression of VCAM-1 on VSMCs and that the interruption of this contact in atheroma is an important pathogenic event. As VCAM-1 not only serves as an adhesion molecule but also as a costimulator of immune cells, its expression may be crucial in the propagation of vascular lesions.

Cell Adhesion↗
PubMed1997

Thrombin stimulates syndecan-1 promotor activity and expression of a form of syndecan-1 that binds antithrombin III in vascular smooth muscle cells.

Vascular smooth muscle (VSM) cells express transmembrane proteoglycans of the syndecan gene family. We reported previously that the expression of syndecans by VSM cells is regulated by mitogens such as serum, platelet-derived growth factor, and basic fibroblast growth factor and that syndecan expression is induced after balloon injury in vivo. We now show that thrombin is a potent inducer of syndecan-1 expression in VSM cells. Transient transfection experiments with a rat syndecan-1 promoter construct demonstrated that thrombin stimulates transcription of the syndecan-1 gene. Syndecan expression in response to thrombin was not inhibited by downregulation of protein kinase C. Thrombin-induced syndecan-1 expression was dependent on tyrosine kinase activity. Calcium was necessary for syndecan-1 expression, but increasing the intracellular calcium levels was not sufficient to induce syndecan-1 expression. Analysis of antithrombin III (AT III) binding activity revealed that thrombin caused an increase in the synthesis of syndecan-1 molecules that exhibited high-affinity AT III binding. These results suggest that VSM cells could play an important role in controlling local thrombus formation subsequent to vascular injury, via a feedback mechanism that involves thrombin-induced stimulation of an inhibitor of thrombin activity.

Animals↗
PubMed1997

Natriuretic peptide family as a novel antimigration factor of vascular smooth muscle cells.

Vascular smooth muscle cell (SMC) migration is proposed to be an important process in the initiation and/or progression of atherosclerosis. The present study examined the effects of the natriuretic peptide family (atrial, brain, and C-type natriuretic peptides; ANP, BNP, and CNP) on the migration of cultured rat SMCs, using Boyden's chamber methods. Fetal calf serum (FCS) and platelet-derived growth factor (PDGF)-BB potently stimulated SMC migration. Rat ANP(1-28), rat BNP-45, and rat CNP-22 clearly inhibited SMC migration stimulated with FCS or PDGF-BB in a concentration-dependent manner. CNP-22 had the most potent inhibitory effect compared with other natriuretic peptides. When PDGF-BB-induced migration was separated into chemotactic and chemokinetic activities, the chemotactic component was strongly inhibited by these natriuretic peptides. Such inhibition by these natriuretic peptides was paralleled by an increase in the cellular level of cyclic GMP. The addition of a cyclic GMP analogue, 8-bromo cyclic GMP, and an activator of the cytosolic guanylate cyclase, sodium nitroprusside, significantly inhibited FCS- and PDGF-BB-stimulated migration in a concentration-dependent manner. These results suggest that natriuretic peptides, especially CNP-22, inhibit FCS- or PDGF-BB-stimulated SMC migration at least in part through a cyclic GMP-dependent process. Thus, the natriuretic peptide family may play a role as an antimigration factor of SMCs under certain circumstances.

Animals↗
PubMed2000

Proliferative effect of lipoprotein lipase on human vascular smooth muscle cells.

Vascular smooth muscle cell (VSMC) proliferation is a key event in the development and progression of atherosclerotic lesions. Accumulating evidence suggests that lipoprotein lipase (LPL) produced in the vascular wall may exert proatherogenic effects. The aim of the present study was to examine the effect of LPL on VSMC proliferation. Incubation of growth-arrested human VSMCs with purified endotoxin-free bovine LPL for 48 and 72 hours, in the absence of any added exogenous lipoproteins, resulted in a dose-dependent increase in VSMC growth. Addition of VLDLs to the culture media did not further enhance the LPL effect. Treatment of growth-arrested VSMCs with purified human or murine LPL (1 microg/mL) led to a similar increase in cell proliferation. Neutralization of bovine LPL by the monoclonal 5D2 antibody, irreversible inhibition, or heat inactivation of the lipase suppressed the LPL stimulatory effect on VSMC growth. Moreover, preincubation of VSMCs with the specific protein kinase C inhibitors calphostin C and chelerythrine totally abolished LPL-induced VSMC proliferation. In LPL-treated VSMCs, a significant increase in protein kinase C activity was observed. Treatment of VSMCs with heparinase III (1 U/mL) totally inhibited LPL-induced human VSMC proliferation. Taken together, these data indicate that LPL stimulates VSMC proliferation. LPL enzymatic activity, protein kinase C activation, and LPL binding to heparan sulfate proteoglycans expressed on VSMC surfaces are required for this effect. The stimulatory effect of LPL on VSMC proliferation may represent an additional mechanism through which the enzyme contributes to the progression of atherosclerosis.

Alkaloids↗
PubMed1997

Dopamine D1-like receptor stimulation inhibits hypertrophy induced by platelet-derived growth factor in cultured rat renal vascular smooth muscle cells.

Vascular smooth muscle cell (VSMC) hypertrophy is believed to play some roles in atherosclerosis. To elucidate the role of vascular D1-like receptors in VSMC hypertrophy, the effects of dopamine and specific D1-like receptor agonists SKF 38393 and YM 435 on platelet-derived growth factor (PDGF) BB-mediated VSMC hypertrophy was studied. We observed that cells stimulated by PDGF-BB 5 ng/mL showed increased VSMC hypertrophy. These effects were prevented by coincubation with dopamine, SKF 38393, and YM 435 1-10 mumol/L, and this prevention was reversed by Sch 23390 1 to 10 mumol/L, a specific D1-like receptor antagonist. These actions are mimicked by forskolin 1 to 10 mumol/L, a direct activator of adenylate cyclase and 8-bromo-cAMP 0.1 to 1 mmol/L, and are blocked by a specific protein kinase A (PKA) inhibitor N-[2-(P-bromcoinnamylamino)ethyl]-5-isoquinoline-sulfonamide (H89) but not blocked by its negative control. PDGF-BB (5 ng/mL)-mediated mitogen-activated protein kinase (MAPK) activity was significantly suppressed by coincubation with D1-like receptor agonists, which were reversed by PKA inhibitor H 89. These results suggest that vascular D1-like receptor agonists inhibit hypertrophy of VSMC, possibly through PKA activation and suppression of activated MAPK activity.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1988

Na+-Ca2+ exchange in cultured vascular smooth muscle cells.

Vascular smooth muscle cells (VSMC) contract as intracellular free calcium ([Ca2+]i) rises. While Na+-Ca2+ exchange has been proposed to contribute to transmembrane Ca2+ flux, its role in cultured VSMC is unknown. Accordingly, we have investigated the role of Na+-Ca2+ exchange in unidirectional and net transmembrane Ca2+ fluxes in cultured rat aortic VSMC under basal conditions and following agonist-mediated stimulation. Transmembrane Ca2+ uptake was significantly increased in response to a low external Na+ concentration ([Na+]o) compared with 140 mM [Na+]o. Na+-dependent Ca2+ uptake in response to low [Na+]o was further increased by intracellular Na+ loading by preincubation of the VSMC with 1 mM ouabain. Under steady-state conditions, Ca2+ content varied inversely with [Na+]o, increasing from 1.0 nmol Ca2+/mg protein at 140 mM [Na+]o to 4.0 nmol Ca2+/mg protein at 20 mM [Na+]o. Increasing [K+]o to 55 mM also enhanced Na+-dependent Ca2+ influx. Augmentation of Ca2+ uptake with K+ depolarization was not significantly inhibited by the calcium channel antagonist verapamil. Transmembrane Ca2+ efflux was increased in response to 130 mM [Na+]o compared with zero [Na+]o (iso-osmotic substitution with choline+), and was further stimulated by the vasoconstrictor angiotensin II, which is known to elevate [Ca2+]i. These changes in [Ca2+]i were studied directly using fura-2 fluorescence measurements. Elevated [Ca2+]i levels returned to baseline more rapidly in the presence of normal (130 mM) [Na+]o compared with zero [Na+]o (iso-osmotic substitution with choline+). These findings suggest that a bidirectional Na+-Ca2+ exchange mechanism is present in cultured rat aortic VSMC.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1998

Prostaglandin D2 inhibits inducible nitric oxide synthase expression in rat vascular smooth muscle cells.

Vascular smooth muscle cells (VSMCs) as well as macrophages have been shown to generate a substantial amount of NO in inflammatory vascular lesions. Prostaglandin (PG) D2 (PGD2) is produced by inflammatory cells, including mast cells and macrophages. We investigated whether PGD2 modulates NO metabolism in rat VSMCs. PGD2 at a concentration of 10(-7) mol/L or greater dose-dependently inhibited nitrite accumulation in the medium of cultured VSMCs stimulated with interleukin 1beta (IL-1beta). In a dose-response analysis of IL-1beta and nitrite accumulation, PGD2 was seen to decrease the maximal ability of VSMCs to generate NO, arguing against competition by PGD2 at cytokine receptors. Northern analysis showed that PGD2 suppresses induction of inducible NO synthase (iNOS) mRNA in IL-1beta-stimulated VSMCs, with consequent inhibition of iNOS protein expression in Western analysis. A thromboxane A2 (TXA2) analogue, U46619 (10(-5) mol/L), produced less inhibition of NO generation than did PGD2. Neither the PGI2 analog carbaprostacyclin nor PGE1 showed any inhibition. PGD2 dose-dependently inhibited NO generation despite the addition of the TXA2 antagonist SQ29548. PGJ2, delta12-PGJ2, and 15-deoxy-delta12,14-PGJ2, all metabolites of PGD2, were as potent as or slightly stronger than PGD2 in the inhibition of NO generation. These data suggest that PGD2 suppresses NO generation in VSMCs by inhibiting iNOS mRNA expression, most likely through the cascade of the PGJ2 series rather than through the TX receptor or cAMP upregulation. Such action makes it likely that PGD2 regulates NO metabolism in vascular lesions.

Animals↗
PubMed2000

Tumor necrosis factor-alpha enhances mRNA expression and secretion of interleukin-6 in cultured human airway smooth muscle cells.

Airway smooth muscle (ASM) is considered to be an end-target cell for the effects of mediators released during airway wall inflammation. Several reports suggest that activated ASM may be capable of generating various proinflammatory cytokines. We investigated the effects of tumor necrosis factor (TNF)-alpha, a potent proinflammatory cytokine, on cultured human ASM cells by examining the expression and release of the cytokine interleukin (IL)-6, cell proliferation, and the expression pattern of c-fos and c-jun, two nuclear proto-oncogenes constituting the activator protein-1 transcription factor. Growth-arrested cell monolayers were stimulated with human recombinant TNF-alpha in a concentration- and time-dependent manner. TNF-alpha stimulated the expression of IL-6 messenger RNA (mRNA), which was detected after 15 min, reaching a maximum at 1 h. IL-6 protein was readily detected in ASM cell-conditioned medium after 2 h of TNF-alpha stimulation. Protein levels increased in a time- and concentration-dependent manner. Release of IL-6 elicited by TNF-alpha was significantly inhibited by dexamethasone, cycloheximide, and nordihydroguaiaretic acid (NDGA). TNF-alpha did not alter DNA biosynthesis up to 48 h or cell numbers up to 120 h. Northern blot analysis of proto-oncogene expression revealed that c-fos and c-jun mRNA levels were elevated after 30 min of TNF-alpha incubation with maximum levels at 1 h and 45 min, respectively. Expression of c-fos mRNA was downregulated by NDGA. Four hours of TNF-alpha treatment resulted in translocation of c-jun immunofluorescence from the cytoplasm to the nucleus in human ASM cells. Our results suggest that despite the lack of a mitogenic response to TNF-alpha, upregulation of primary response genes in human ASM cells may account for the induction of proinflammatory cytokines, such as IL-6, in human airways.

Bronchi↗
PubMed1994

Structure-activity relationship of adrenomedullin, a novel vasodilatory peptide, in cultured rat vascular smooth muscle cells.

Vascular smooth muscle cells (VSMC) from rat aorta possess specific receptors for a novel potent vasorelaxant peptide, adrenomedullin (AM). To elucidate its receptor coupling to guanine nucleotide-binding stimulatory protein and the structural requirement of the AM molecule to its vascular receptors, we have studied the effects of guanine nucleotides on [125I]human (h) AM binding and adenylate cyclase activity in cultured rat VSMC, and the effects of various synthetic hAM analogs on [125I]hAM binding and the cAMP response. Guanosine 5'-O-(3-thiotriphosphate) dose dependently inhibited [125I]hAM binding to rat VSMC membranes. hAM stimulated adenylate cyclase activity, and its effect was additive with GTP. hAM-induced cAMP formation was abrogated by pretreatment with cholera toxin, but not by that with pertussis toxin. Intact hAM-(1-52)-NH2 and N-terminal truncated derivatives [hAM-(13-52)-NH2, hAM-(16-52)-NH2] almost equally inhibited [125I]hAM binding and stimulated cAMP formation, whereas removal of C-terminal Tyr52 residue [hAM-(1-51)-NH2] remarkably decreased receptor-binding activity and the cAMP response. The effects of hAM-(1-52)-OH, hAM-(1-51)-OH, and a linear hAM analog ([carbamoylmethyl-Cys16,21]hAM-NH2) were far less potent on receptor binding and the cAMP response than that of hAM-(1-52)-NH2. The C-terminal fragment [hAM-(33-52)-NH2] and the N-terminal fragment [hAM-(1-10)-OH] had neither receptor-binding nor adenylate cyclase activity. hAM-(22-52)-NH2 had no agonistic effect, but showed an antagonistic effect on the hAM-induced cAMP response. These data suggest that vascular AM receptors are functionally coupled to adenylate cyclase via guanine nucleotide-binding stimulatory protein. Studies of the structure-activity relationship of hAM revealed that the cyclic structure formed by the disulfide bridge and amidation of the C-terminal residue of the AM molecule are critical for receptor binding and subsequent cAMP generation and suggest that the C-terminal fragment hAM-(22-52)-NH2 may be an antagonist for vascular AM receptors.

Adenylate Cyclase Toxin↗
PubMed1989

Insulin, insulin-like growth factor I and platelet-derived growth factor interact additively in the induction of the protooncogene c-myc and cellular proliferation in cultured bovine aortic smooth muscle cells.

Vascular smooth muscle cell (SMC) growth is under the influence of various growth factors. We demonstrate that platelet-derived growth factor (PDGF) stimulates DNA synthesis of cultured bovine aortic SMCs by 2.5- to 3.5-fold. PDGF also exhibits additivity with insulin and insulin-like growth factor I (IGF-I) for DNA synthesis and cellular proliferation. Insulin (2 x 10(-6) M), IGF-I (1 x 10(-8) M), and PDGF (1 x 10(-9) M) cause a 60-80% increase in cell numbers over basal, but PDGF with insulin or IGF causes a 40-150% increase over basal. No additivity between insulin and IGF-I is evident. PDGF also induces commitment to DNA synthesis earlier than insulin or IGF-I. After exposure to PDGF for 4 h, SMCs incorporate 3H-thymidine to 60% of maximum (with PDGF alone) levels (achieved after exposure of 12 h or longer). Insulin and IGF-I exposure for 4 h, on the other hand, achieves 3H-thymidine incorporation that is only a 20-30% of maximum (with insulin or IGF-I alone). Insulin, IGF-I, and PDGF increase mRNA levels of the protooncogene c-myc. This induction begins within 30 min of exposure to these growth factors which causes a 4- to 6-fold increase in c-myc mRNA levels. Additivity is also observed between PDGF with insulin or IGF-I, but not between insulin or IGF-I, in c-myc induction. C-myc mRNA levels remain elevated as long as the hormones are present, although there's a tendency for the mRNA levels to fall off with insulin and IGF-I.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Endothelin-1, superoxide and adeninediphosphate ribose cyclase in shark vascular smooth muscle.

In vascular smooth muscle (VSM) of Squalus acanthias, endothelin-1 (ET-1) signals via the ET(B) receptor. In both shark and mammalian VSM, ET-1 induces a rise in cytosolic Ca(2+) concentration ([Ca(2+)](i)) via activation of the inositol trisphosphate (IP(3)) receptor (IP(3)R) and subsequent release of Ca(2+) from the sarcoplasmic reticulum (SR). IP(3)R-mediated release of SR Ca(2+) causes calcium-induced calcium release (CICR) via the ryanodine receptor (RyR), which can be sensitized by cyclic adeninediphosphate ribose (cADPR). cADPR is synthesized from NAD(+) by a membrane-bound bifunctional enzyme, ADPR cyclase. We have previously shown that the antagonists of the RyR, Ruthenium Red, high concentrations of ryanodine and 8-Br cADPR, diminish the [Ca(2+)](i) response to ET-1 in shark VSM. To investigate how ET-1 might influence the activity of the ADPR cyclase, we employed inhibitors of the cyclase. To explore the possibility that ET-1-induced production of superoxide (O(2)*-) might activate the cyclase, we used an inhibitor of NAD(P)H oxidase (NOX), DPI and a scavenger of O(2)*-, TEMPOL. Anterior mesenteric artery VSM was loaded with fura-2AM to measure [Ca(2+)](i). In Ca(2+)-free shark Ringers, ET-1 increased [Ca(2+)](i) by 104+/-8 nmol l(-1). The VSM ADPR cyclase inhibitors, nicotinamide and Zn(2+), diminished the response by 62% and 72%, respectively. Both DPI and TEMPOL reduced the response by 63%. The combination of the IP(3)R antagonists, 2-APB or TMB-8, with DPI or TEMPOL further reduced the response by 83%. We show for the first time that in shark VSM, inhibition of the ADPR cyclase reduces the [Ca(2+)](i) response to ET-1 and that superoxide may be involved in the activation of the cyclase.

ADP-ribosyl Cyclase↗
PubMedDate not supplied

Metabolic effects of direct current stimulation on cultured vascular smooth muscle cells.

Vascular smooth muscle cells from rabbit arteries were grown in tissue culture and stimulated by DC impulses (1 mA, 1 V, 10 Hz, 1 ms/imp). Scanning microscopic examination disclosed that in stimulated cultures the cell surface was enlarged by numerous microvilli. This was interpreted as being indicative of an increase in cell activity. Cellular metabolism was characterized by analyzing the incubation medium for glucose, glutamate/glutamine, and lactate. When compared to unstimulated controls, stimulation caused an increase in the uptake of glucose and glutamine as well as an increased lactate production. The enhancing effect on metabolism was prevented when the "calcium antagonist" verapamil was present (5 X 10(-6) M). Although the exact mechanism by which DC stimulation influences the cells remains obscure, this finding indicates an important mediating role of Ca2+ ions.

Animals↗
PubMed2004

Ca2+ entry, efflux and release in smooth muscle.

Control of smooth muscle is vital for health. The major route to contraction is a rise in intracellular [Ca2+], determined by the entry and efflux of Ca2+ and release and re-uptake into the sarcoplasmic reticulum (SR). We review these processes in myometrium, to better understand excitation-contraction coupling and develop strategies for preventing problematic labours. The main mechanism of elevating [Ca2+] is voltage-gated L-type channels, due to pacemaker activity, which can be modulated by agonists. The rise of [Ca2+] produces Ca-calmodulin and activates MLCK. This phosphorylates myosin and force results. Without Ca2+ entry uterine contraction fails. The Na/Ca exchanger (NCX) and plasma membrane Ca-ATPase (PMCA) remove Ca2+, with contributions of 30% and 70% respectively. Studies with PMCA-4 knockout mice show that it contributes to reducing [Ca2+] and relaxation. The SR contributes to relaxation by vectorially releasing Ca2+ to the efflux pathways, and thereby increasing their rates. Agonists binding produces IP3 which can release Ca from the SR but inhibition of SR Ca2+ release increases contractions and Ca2+ transients. It is suggested that SR Ca2+ targets K+ channels on the surface membrane and thereby feedback to inhibit excitability and contraction.

Animals↗
PubMed1991

Action of acetylcholine on smooth muscle.

Contraction of smooth muscle by acetylcholine is mediated by activation of muscarinic receptors of which M2 and M3 subtypes are present in longitudinal muscle of guinea pig intestine. In single cells, muscarinic receptor activation evokes calcium release from stores which raises the internal free calcium concentration and causes opening of calcium-activated potassium channels. The rise in internal calcium suppresses the voltage-dependent inward calcium current. A third important effect is the opening of channels which cause depolarization of the membrane and so increase action potential discharge and contraction in the whole muscle. These channels were studied by voltage-clamp of single cells from longitudinal muscle of rabbit small intestine. They were found to be permeable to Na and K but not detectably permeable to Cl. They can pass Ca but the amount entering the cell is not sufficient to raise the internal calcium concentration appreciably.

Acetylcholine↗
PubMed1990

Diversity of rhythmicity in gastrointestinal smooth muscles.

Diversity in smooth muscles is well shown by differences in gastrointestinal rhythms. Basic rhythmic activity apparently occurs only when there is interaction between clusters of cells. It is postulated that the oscillations of basic electrical rhythms result from action of a membrane ionic network. In addition to slow waves, gastrointestinal muscle is capable of acetylcholine-induced rhythms, of spontaneous "slow spikes" that may be similar to the Ca2+ component in stomach, of neurally paced migrating complexes, of Ca-EGTA plateaus and of stretch induced rhythms.

Acetylcholine↗
PubMed1986

Regulation of cytoplasmic Ca2+ in vascular smooth muscle.

The vascular smooth muscle of conduit arteries can be excited by either depolarization or agonists. The former stimulus opens potential sensitive Ca2+ channels in the plasmalemma and releases bound Ca2+ from its outer surface. Ne interacts with alpha-receptors to open receptor operated Ca2+ channels which are distinct from the PSCs and also liberates surface bound Ca2+. In addition, it releases "trigger" Ca2+ from the inner plasmalemmal surface which in turn induces Ca2+ release from the sarcoplasmic reticulum. The elevated cytoplasmic free Ca2+ then combines with calmodulin to stimulate myosin light-chain kinase.

Animals↗