Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carbachol increased ventricular automaticity in a concentration-dependent fashion from a control rate of 72 +/- 5 (mean +/- SEM) to 86 +/- 4 beats per minute at 10(-4) M carbachol. Pirenzepine, an M1-selective antagonist, and AFDX 116, an M2-selective antagonist, both at 10(-7) M, did not block the carbachol-induced positive chronotropic response. In contrast, 10(-7) M HHSiD, an M3-selective antagonist, completely blocked the positive chronotropic effect of carbachol. Carbachol stimulated the accumulation of IP1 in a concentration-dependent manner at concentrations > or = 3 x 10(-6) M. AFDX 116 had no effect on carbachol-induced IP1 accumulation. HHSiD significantly inhibited IP1 accumulation at concentrations > or = 3 x 10(-8) M, while pirenzepine inhibited IP1 accumulation only at concentrations > or = 10(-5) M. McN A343 and methacholine, two muscarinic receptor agonists with minimal M2 activities, and carbachol did not alter basal cAMP concentration, but all three agonists significantly attenuated the increase in cAMP accumulation in response to isoproterenol. Carbachol inhibited isoproterenol-mediated cAMP accumulation at concentrations > or = 10(-7) M. AFDX 116, HHSiD, and pirenzepine blocked the carbachol-induced inhibition of isoproterenol-stimulated cAMP accumulation. At equimolar concentrations, the inhibitory effects of HHSiD and AFDX-116 were similar, while that of pirenzepine was much less. Pretreatment with pertussis toxin for 24 h did not prevent the carbachol-mediated positive chronotropic response or accumulation of IP1 but completely abolished the inhibition of isoproterenol-stimulated cAMP accumulation. These results indicate that (a) neonatal ventricular myocytes in culture have a heterogeneous population of muscarinic (M2 and M3) receptors, (b) the M3 receptor is coupled to pertussis toxin-sensitive and pertussis toxin-insensitive G proteins, (c) M3 receptor stimulation activates phosphoinositide hydrolysis and increases automaticity via a pertussis toxin-insensitive G protein-dependent pathway, and (d) both M2 and M3 receptors couple to pertussis toxin-sensitive G protein(s) to mediate the inhibition of intracellular cAMP accumulation in response to isoproterenol stimulation.
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PMID:Muscarinic receptor heterogeneity in neonatal rat ventricular myocytes in culture. 884 59

In order to investigate the mechanisms responsible for the inotropic effects of muscarinic acetylcholine receptor stimulation by high concentrations of muscarinic receptor agonists, we studied the effects of carbachol at 30-300 microM on the electrically induced [Ca2+]i transient of rat isolated ventricular myocytes. Carbachol at this dose range increased the amplitude and duration of the electrically induced [Ca2+]i transient time and dose dependently. It also increased the resting fluorescence ratio and time to 80% decline of amplitude from the peak. At 100-300 microM the increase in [Ca2+]i transient was followed by a cluster of Ca2+ oscillations in 50-83% of the cells studied. The effects were blocked by atropine, but not pertussis toxin. Depletion of Ca2+ from sarcoplasmic reticulum by ryanodine, which itself reduced the amplitude of the [Ca2+]i transient and increase resting fluorescence, abolished the effect of carbachol on the [Ca2+]i transient without affecting its effect on resting fluorescence ratio. The caffeine-induced [Ca2+]i transient was unaffected by prior addition of carbachol in a Ca2+ free and low Na+ solution. Inhibition of Ca2+ by the L-type Ca2+ channel blocker, verapamil, which itself reduced the amplitude of the [Ca2+]i transient without affecting the resting fluorescence ratio, attenuated the augmentation of the amplitude of the [Ca2+]i transient elicited by carbachol. Ni2+, a non-specific Ca2+ channel blocker and an inhibitor of Na(+)-Ca2+ exchange, abolished the effects of carbachol on both [Ca2+]i transient and resting fluorescence ratio. Low external Na+, which increased the resting fluorescence ratio due to its inhibitory effect on Na(+)-Ca2+ exchange, also abolished the effects of carbachol. The results indicate that the inotropic effect of muscarinic acetylcholine receptor stimulation by high concentrations of a muscarinic receptor agonist may be due to an increase in the electrically induced [Ca2+]i transient in ventricular myocytes via a process which is not pertussis toxin sensitive. The increase in the electrically induced [Ca2+]i transient may result from increases in Na2(+)-Ca2+ exchange and influx of Ca2+ via voltage-gated Ca2+ channels, and mobilization of Ca2+ from the intracellular store. The mobilization of Ca2+ from the intracellular store is a secondary event. The study has provided for the first time that muscarinic acetylcholine receptor stimulation by high concentrations of carbachol increases Ca2+ influx via the Ca2+ channel and mobilization of Ca2+ from its intracellular store. The study has also demonstrated for the first time the occurrence of Ca2+ oscillations induced by high concentrations of carbachol.
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PMID:High carbachol increases the electrically induced [Ca2+]i transient in the single isolated ventricular myocyte of rats. 903 Sep 3

Hamster tracheal epithelial cell cultures were used to investigate muscarinic regulation of high-molecular-weight glycoconjugate (HMWG) secretion by airway goblet cells. HMWG were radiolabeled with N-acetyl-D-[1-(3)H]glucosamine, precipitated with trichloroacetic acid and phosphotungstic acid, and counted by liquid scintillation. Carbachol (100 microM) increased HMWG secretion (166.6 +/- 18.7%, P < 0.001, n = 20), and this response was blocked by the muscarinic receptor antagonist atropine. Ca2+ may not be essential for carbachol response since 1) carbachol-activated secretion was not inhibited by chelating extracellular Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) or by reducing both extracellular and intracellular Ca2+ with BAPTA-acetoxymethyl ester in low-Ca2+ medium; 2) the carbachol response was only partially blocked in low-Ca2+ medium; and 3) calcium ionophore did not stimulate HMWG secretion. However, carbachol-stimulated secretion was abolished by pertussis toxin (PTX), indicating the involvement of a PTX-sensitive guanine nucleotide-binding regulatory protein (G protein), and by the protein kinase C (PKC) inhibitor chelerythrine chloride. Furthermore, carbachol-stimulated secretion was not inhibited by overnight incubation with phorbol 12-myristate 13-acetate. In conclusion, carbachol-stimulated secretion of HMWG appears to be coupled to a PTX-sensitive G protein and requires the activation of a phorbol ester-insensitive PKC isoform.
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PMID:Muscarinic-induced mucin secretion and intracellular signaling by hamster tracheal goblet cells. 912 73

Cardiac muscarinic receptors activate an inwardly rectifying K+ channel, IK+Ach, via pertussis toxin (PT)-sensitive heterotrimeric G proteins (in heart Gi2, Gi3, or Go). We have used embryonic stem cell (ES cell)-derived cardiocytes with targeted inactivations of specific PT-sensitive alpha subunits to determine which G proteins are required for receptor-mediated regulation of IK+Ach in intact cells. The muscarinic agonist carbachol increased IK+Ach activity in ES cell-derived cardiocytes from wild-type cells, in cells lacking alphao, and in cells lacking the PT-insensitive G protein alphaq. In cells with targeted inactivation of alphai2 or alphai3, channel activation by both carbachol and adenosine was blocked. Carbachol-induced channel activation was restored in the alphai2- and alphai3-null cells by reexpressing the previously targeted gene and guanosine 5'-[gamma-thio] triphosphate was able to fully activate IK+Ach in excised membranes patches from these mutants. In contrast, negative chronotropic responses to both carbachol and adenosine were preserved in cells lacking alphai2 or alphai3. Our results show that expression of two specific PT-sensitive alpha subunits (alphai2 and alphai3 but not alphao) is required for normal agonist-dependent activation of IK+Ach and suggest that both alphai2- and alphai3-containing heterotrimeric G proteins may be involved in the signaling process. Also the generation of negative chronotropic responses to muscarinic or adenosine receptor agonists do not require activation of IK+Ach or the expression of alphai2 or alphai3.
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PMID:Targeted inactivation of alphai2 or alphai3 disrupts activation of the cardiac muscarinic K+ channel, IK+Ach, in intact cells. 922 88

Neonatal rat ventricular myocytes express both beta 1-and beta 2-adrenergic receptors linked to enhanced intracellular adenosine 3',5'-cyclic monophosphate (cAMP) accumulation and the modulation of contractile function. This study tests the hypothesis that muscarinic agonists act via distinct mechanisms to interfere with beta 1-and beta 2-adrenergic receptor actions. The beta 2-selective agonist zinterol (10(-7) M) elicits approximately a fourfold increase in cAMP accumulation, which is mimicked, both in magnitude and kinetics, by 10(-9) M of the mixed beta 1-receptor agonist/beta 2-receptor agonist isoproterenol. At these concentrations, isoproterenol and zinterol elicit equivalent inotropic and lusitropic (i.e., enhanced relaxation) responses. Carbachol inhibits all three responses (cAMP, inotropic, and lusitropic) elicited by isoproterenol. In contrast, carbachol does not interfere with the effect of zinterol to augment cAMP accumulation or to induce a positive inotropic response. However, carbachol inhibits the lusitropic response to zinterol via an action at an M2-muscarinic receptor linked to a pertussis toxin-sensitive pathway. Additional studies indicate that beta 2-receptor-dependent phosphorylation of troponin I and phospholamban is substantially attenuated by carbachol. We conclude that carbachol interferes with beta 1-receptor actions by reducing cAMP accumulation. In contrast, the anti-beta 2-receptor actions of carbachol are mediated by a mechanism that is distinct from inhibition of cAMP accumulation, involving an M2-muscarinic receptor coupled to a pertussis toxin-sensitive G protein, which leads to inhibition of troponin I and phospholamban phosphorylation and inhibition of the beta 2-receptor-dependent lusitropic response.
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PMID:beta 1-and beta 2-adrenergic receptors exhibit differing susceptibility to muscarinic accentuated antagonism. 922 52

The purpose of this study was to visualize muscarinic receptors and their distribution on cardiomyocytes and to examine the effects of muscarinic cholinergic receptor (mACh-R) stimulation with carbachol on phosphatidylcholine hydrolysis. Cardiomyocytes were prepared as primary culture from 7-day-old chick embryo hearts. Cardiomyocytes, grown on cover slips, were labelled with BODIPY PZ, a fluorescent analog of the muscarinic receptor antagonist pirenzepine, and examined with a laser scanning confocal microscope, mACh-R clusters were visualized and were fairly homogeneous in size with diameters ranging from 0.5 to 1.0 micron. The number of receptor clusters per cell was 83.5 +/- 6.8 (mean +/- SEM) and clusters were found at the periphery of the cell. Cardiomyocytes, grown as a monolayer in dishes, were treated with the 10(-4) M carbachol, a mACh-R agonist, and the effects on phosphatidylcholine hydrolysis were ascertained in cells preincubated with [methyl-3H]choline for 18 h. Cells were washed, lysed, and subjected to thin-layer chromatography to separate [3H]choline in various metabolites of phosphatidylcholine. Carbachol significantly (p < 0.05) increased intracellular free choline and decreased cellular phospholipid consistent with phosphatidylcholine hydrolysis. Carbachol increased the amount of [3H]choline that effluxed out of the cardiomyocyte into the medium. Carbachol-induced choline efflux was not prevented by pretreatment with n-butanol, a phospholipase D inhibitor, suggesting that other lipases such as phospholipase C are the major enzyme involved in phosphatidylcholine hydrolysis. Pertussis toxin prevented carbachol-induced choline efflux and the changes in intracellular free choline and phospholipid. An action of carbachol through G proteins was supported by the ability of pertussis toxin to antagonize the carbachol-induced reduction in cAMP generation from isoproterenol. In summary, mACh-Rs, visualized in living cardiomyocytes, were peripheral to the nucleus. Phosphatidylcholine hydrolysis induced by mACh-R stimulation may be a signal transduction pathway for mACh-R in the cardiomyocyte, operating through inhibitory G proteins sensitive to pertussis toxin.
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PMID:Visualization of muscarinic cholinergic receptors on chick cardiomyocytes and their involvement in phosphatidylcholine hydrolysis. 925 Mar 60

We report here that the M1, M3 and M5 muscarinic acetylcholine receptor subtypes that have been shown to couple to phosphoinositide hydrolysis also activate the mitogen-activated protein kinase (MAPK). Pharmacological characterization as well as mechanistic details of the activation pathway are presented. Carbachol-induced MAPK activation was time- and concentration-dependent at all subtypes. Pharmacological characterization of the MAPK response revealed that McN-A-343 was a partial agonist at the M1 and M3 subtypes, and that pilocarpine was a partial agonist at the M3 and M5 receptors. Carbachol-mediated MAPK activation at these receptor subtypes was pertussis toxin and wortmannin insensitive. By contrast, both agents significantly inhibited carbachol-induced MAPK activation by the M2 muscarinic receptor subtype. Furthermore, two independent single point mutations in the M1 receptor attenuated carbachol-induced activation of MAPK. Activation of MAPK at the M1, M3 and M5 muscarinic receptor subtypes was not dependent on intracellular or extracellular Ca2+, but was partially dependent upon protein kinase C. These data suggest that activation of MAPK by M1, M3 and M5 muscarinic receptors involves protein kinase C-dependent and independent pathways.
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PMID:M1, M3 and M5 muscarinic receptors stimulate mitogen-activated protein kinase. 956 19

The role of G proteins in glucose uptake was investigated using C6 glioma cells. Carbachol (an agonist acting via G protein coupled receptors) and 5'-guanylylimidodiphosphate (Gpp(NH)p; a nonhydrolysable guanine nucleotide analog which bypasses the receptors and directly activates G proteins) stimulated [3H]2-deoxy-D-glucose (2DG) uptake by C6 cells, suggesting that hexose uptake is a G protein-mediated process. To identify the G protein involved in glucose uptake by C6 cells, the effect of carbachol on 2DG uptake was examined in the presence of pertussis toxin. Pertussis toxin treatment did not alter the ability of C6 cells to respond to carbachol, ruling out the involvement of G(i alpha) in 2DG uptake. C6 cells were transfected with G(q alpha) or GLUT1 cDNA for 48 h, exposed to 1 mM carbachol for 2 h, and processed for 2DG uptake. Carbachol stimulated 2DG uptake in both G(q alpha) and GLUT1-transfected cells. Gpp(NH)p, also stimulated 2DG uptake in G(q alpha) and GLUT1-transfected cells. These results suggest that muscarinic receptor coupling to G(q alpha) regulates hexose uptake in C6 cells.
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PMID:Glucose uptake by C6 glioma cells is mediated by G(q alpha). 959 59

To determine whether M2 muscarinic receptors are linked to the monomeric G protein Rho, we studied the effect of carbachol on actin reorganization (stress fiber formation) in cultured human airway smooth muscle cells that expressed mainly M2 muscarinic receptors by dual-fluorescence labeling of filamentous (F) and monomeric (G) actin. F-actin was labeled with FITC-labeled phalloidin, and G-actin was labeled with Texas Red-labeled DNase I. Carbachol stimulation induced stress fiber formation (increased F-actin staining) in the cells and increased the F- to G-actin ratio 3.6 +/- 0.4-fold (mean +/- SE; n = 5 experiments). Preincubation with pertussis toxin, Clostridium C3 exoenzyme, or tyrosine kinase inhibitors reduced the carbachol-induced increase in stress fiber formation and significantly decreased the F- to G-actin ratio, whereas a mitogen-activated protein kinase inhibitor, a phosphatidylinositol 3-kinase inhibitor, and a protein kinase C inhibitor were without effect. This study demonstrates that in cultured human airway smooth muscle cells, muscarinic-receptor activation induces stress fiber formation via a pathway involving a pertussis-sensitive G protein, Rho proteins, and tyrosine phosphorylation.
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PMID:Carbachol-induced actin reorganization involves Gi activation of Rho in human airway smooth muscle cells. 961 96

In many smooth muscle tissues a minor M3-muscarinic acetylcholine (mACh) receptor population mediates contraction, despite the presence of a larger M2-mACh receptor population. However, this is not the case for guinea-pig uterus where radioligand binding and functional studies exclude a dominant role for M3-mACh receptors. Using tissue from animals pre-treated with diethylstilboestrol, estimates of antagonist affinity were made before and after selective alkylation procedures, together with estimates of agonist affinity to characterise the mACh receptor population mediating carbachol-induced contraction of guinea-pig isolated uterus. Antagonist affinity estimates made at 'protected' receptors were not significantly different from those made in untreated tissues. However all estimations were significantly different from those reported in guinea-pig ileum and atria. The rank order of affinities were atropine>zamifenacin=tripitramine> methoctramine. Carbachol-induced contractions were insensitive to the M4-selective muscarinic toxin MTx-3, or PD102807 (0.1 microM) ruling out a role for M4-mACh receptors. The agonist affinity value for L-660,863, a putative 'M2-selective' agonist of 5.44+/-0.30 (n=6) was significantly different from that reported in guinea-pig atria. In contrast, the pKA value for carbachol (4.22+/-0.17 n = 8) agrees with that reported for guinea-pig ileum. Carbachol-induced contractions were insensitive to pertussis toxin although carbachol-induced inhibition of forskolin-stimulated cyclic AMP production was attenuated, ruling out the involvement of Gi-proteins in contraction. Radioligand binding studies revealed a KD for N-[3H]-methylscopolamine of 0.12+/-0.05 nM and a Bmax of 147+/-18 fmol mg protein(-1). Antagonist affinity estimates made using competition binding studies supported previous data suggesting the presence of a homogenous population of M2-mACh receptors. These data suggest a small population of mACh receptors with an atypical operational profile which can not be distinguished using radioligand binding studies may mediate carbachol-induced contraction of guinea-pig isolated uterus.
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PMID:Characterization of an atypical muscarinic cholinoceptor mediating contraction of the guinea-pig isolated uterus. 975 76


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