Stimulation of acid secretion and phosphoinositol production by rat parietal cell muscarinic M2 receptors

The muscarinic receptor system involved in hydrogen ion production by enriched rat gastric parietal cells was investigated. Muscarinic receptor density determined by [N-methyl-3H]scopolamine binding was 8,100/cell. The receptor appeared to be of the M2 muscarinic receptor subtype, since it had a low affinity (Kd, 189 nM) for the M1 receptor antagonist pirenzepine compared with atropine (Kd, 0.74 nM). Receptor activation by carbachol rapidly augmented levels of polyphosphoinositides, indicating an activation of a phospholipase C. The dose-response relations for the increase in inositol phosphates closely paralleled the binding of carbachol to muscarinic receptors with a Km of 17 microM. The inositol phosphate response was antagonized by pirenzepine with a Ki of 177 nM. The stimulation of inositol phosphate levels by carbachol correlated well with the stimulation of [14C]aminopyrine uptake, determined as an index of acid secretion. The muscarinic agonists oxotremorine, pilocarpine, and bethanechol elicited partial increases in inositol phosphates at maximal drug concentrations, and these partial increases correlated with their ability to stimulate [14C]aminopyrine uptake. These data indicate that inositol polyphosphates may be a second messenger of M2 receptors stimulating acid secretion.

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Adrenergic stimulation of inositol phosphate accumulation in tracheal epithelium

Journal of Applied Physiology ◽

10.1152/jappl.1989.66.1.504 ◽

1989 ◽

Vol 66 (1) ◽

pp. 504-508 ◽

Cited By ~ 3

Author(s):

T. Bainbridge ◽

R. D. Feldman ◽

M. J. Welsh

Keyword(s):

Adrenergic Receptor ◽

Inositol Phosphates ◽

Inositol Phosphate ◽

Second Messengers ◽

Receptor Activation ◽

Adrenergic Stimulation ◽

Cl Secretion ◽

Phosphate Accumulation ◽

Inositol Phosphate Accumulation ◽

Stimulation Of

To determine whether inositol phosphates are important second messengers in the regulation of Cl- secretion by airway epithelia, we examined the relationship between inositol phosphate accumulation and Cl- secretion in response to adrenergic agonists. We found that epinephrine stimulated Cl- secretion and inositol phosphate accumulation with similar concentration dependence. Although isoproterenol stimulated Cl- secretion, there was no effect of beta-adrenergic receptor activation on inositol phosphate accumulation. In contrast, alpha 1-adrenergic receptor activation stimulated inositol phosphate accumulation but failed to induce Cl- secretion. Another Cl- secretagogue, prostaglandin E1, also failed to stimulate inositol phosphate accumulation. These data suggest that inositol phosphate accumulation is neither sufficient nor required for stimulation of Cl- secretion in cultured canine tracheal epithelial cells.

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Rapid accumulation and sustained turnover of inositol phosphates in cerebral-cortex slices after muscarinic-receptor stimulation

Biochemical Journal ◽

10.1042/bj2600237 ◽

1989 ◽

Vol 260 (1) ◽

pp. 237-241 ◽

Cited By ~ 14

Author(s):

I H Batty ◽

S R Nahorski

Keyword(s):

Cerebral Cortex ◽

Muscarinic Receptor ◽

Metabolic Flux ◽

Inositol Phosphates ◽

Inositol Phosphate ◽

Receptor Activation ◽

Inositol Polyphosphate ◽

Receptor Stimulation ◽

Cortex Slices ◽

Rapid Kinetics

The rapid kinetics of [3H]inositol phosphate accumulation and turnover were examined in rat cerebral-cortex slices after muscarinic-receptor stimulation. Markedly increased [3H]inositol polyphosphate concentrations were observed to precede significant stimulated accumulation of [3H]inositol monophosphate. New steady-state accumulations of several 3H-labelled products were achieved after 5-10 min of continued agonist stimulation, but were rapidly and effectively reversed by subsequent receptor blockade. The results show that muscarinic-receptor activation involves phosphoinositidase C-catalysed hydrolysis initially of polyphosphoinositides rather than of phosphatidylinositol. Furthermore, prolonged carbachol stimulation is shown not to cause receptor desensitization, but to allow persistent hydrolysis of [3H]phosphatidylinositol bisphosphate and permit sustained metabolic flux through the inositol tris-/tetrakis-phosphate pathway.

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Muscarinic-receptor stimulation enhances polyphosphoinositide breakdown in guinea-pig ileum smooth muscle

Biochemical Journal ◽

10.1042/bj2230527 ◽

1984 ◽

Vol 223 (2) ◽

pp. 527-531 ◽

Cited By ~ 24

Author(s):

M C Sekar ◽

B D Roufogalis

Keyword(s):

Guinea Pig ◽

Muscarinic Receptor ◽

Longitudinal Muscle ◽

Inositol Phosphates ◽

Inositol Phosphate ◽

Exchange Chromatography ◽

Guinea Pig Ileum ◽

Receptor Stimulation ◽

Inositol 1 ◽

Stimulation Of

Muscarinic-receptor stimulation by 0.1 mM-carbachol in longitudinal muscle of the guinea-pig ileum increases the incorporation of [3H]inositol into inositol-containing phospholipid. This effect was blocked by 16 microM-atropine. After 60 min incubation, carbachol increased the accumulation of total inositol phosphates 20-fold in the presence of 10 mM-Li+. Less than 20% of the total inositol phosphate corresponded to inositol 1-phosphate by ion-exchange chromatography, whereas of the remainder about two-thirds corresponded to inositol bisphosphate and one third to inositol trisphosphate. It is concluded that stimulation of muscarinic receptors in guinea-pig ileum enhances breakdown of polyphosphoinositides, suggesting that this may be a primary event associated with Ca2+ mobilization in the guinea-pig ileum.

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Differential regulation of cholecystokinin- and muscarinic-receptor-mediated phosphoinositide turnover in Flow 9000 cells

Biochemical Journal ◽

10.1042/bj2510625 ◽

1988 ◽

Vol 251 (3) ◽

pp. 625-630 ◽

Cited By ~ 8

Author(s):

W W Y Lo ◽

J Hughes

Keyword(s):

G Protein ◽

Muscarinic Receptor ◽

Feedback Inhibition ◽

Inositol Phosphate ◽

Binding Capacity ◽

Second Messenger ◽

Receptor Activation ◽

Maximal Response ◽

Muscarinic Agonist ◽

Stimulation Of

We have explored the hypothesis that the apparent greater efficiency of cholecystokinin (CCK-8) receptor-second messenger coupling compared with that of muscarinic receptor in Flow 9000 cells is due to differential feedback inhibitory control mechanisms. Pretreatment of Flow 9000 cells with the tumour-promoting protein kinase C (PKC)-activating agent 12-O-tetradecanoylphorbol 13-acetate (TPA) produced a time- and dose-dependent inhibition of CCK-8 and acetylcholine (ACh) stimulation of inositol phosphate production. The inhibition by TPA of ACh-induced PI (phosphoinositide) response involved reduction of the maximal response, but no change in the concentration of ACh required to evoke a half-maximal response. In contrast, TPA inhibition of CCK-8 responses could be overcome by increasing the CCK-8 concentrations. Flow 9000 cells pretreated with TPA exhibited a 52-68% reduction in [3H]quinuclidinyl benzilate ([3H]QNB) binding capacity, whereas [125I]CCK-8 binding was unchanged. In saponin-permeabilized Flow 9000 cells, TPA pretreatment had no effect on guanosine 5′-[gamma-thio]triphosphate (GTP[S])-induced inositol phosphate formation, indicating that G-protein linkage to phosphoinositidase C (PIC) was not affected. However, TPA significantly inhibited the potentiating effect of GTP[S] on CCK-8 and ACh activation of PI response, suggesting that the coupling between the receptors and the G-protein was impaired. The PKC-activator 1-oleoyl-2-acetylglycerol (OAG), a diacylglycerol analogue, also significantly reduced CCK-8 and ACh stimulation of inositol phosphate accumulation in these cells. Our results are consistent with the hypothesis that muscarinic activation of PI hydrolysis is subjected to rapid feedback inhibition via the 1,2-diacylglycerol-PKC pathway. CCK-receptor activation of PI turnover is modulated to a lesser extent, and this may partially explain apparent differences in the efficiency of receptor-second messenger coupling. It is proposed that TPA acting through PKC exerts its inhibitory action on muscarinic-agonist-mediated PI response mainly at the receptor level, whereas the inhibitory effect on CCK-8 response is at a site close to the receptor-G-protein coupling step.

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Eicosapentaenoic Acid Interferes with U46619-Stimulated Formation of Inositol Phosphates in Washed Rabbit Platelets

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647129 ◽

1989 ◽

Vol 62 (04) ◽

pp. 1116-1120 ◽

Cited By ~ 9

Author(s):

N Chetty ◽

J D Vickers ◽

R L Kinlough-Rathbone ◽

M A Packham ◽

J F Mustard

Keyword(s):

Signal Transduction ◽

Fatty Acid Composition ◽

Eicosapentaenoic Acid ◽

Inositol Phosphates ◽

Inositol Phosphate ◽

Dense Granule ◽

Detectable Change ◽

Membrane Phospholipids ◽

Rabbit Platelets ◽

Stimulation Of

SummaryEicosapentaenoic acid (EPA) inhibits platelet responsiveness to aggregating agents. To investigate the reactions that are affected by EPA, we examined the effect of preincubating aspirintreated rabbit platelets with EPA on stimulation of inositol phosphate formation in response to the TXA2 analogue U46619. Stimulation of platelets with U46619 (0.5 μM) caused aggregation and slight release of dense granule contents; aggregation and release were inhibited by preincubation of the platelets with EPA (50 μM) for 1 h followed by washing to remove unincorporated EPA. Incubation with EPA (50 μM) for 1 h did not cause a detectable increase in the amount of EPA in the platelet phospholipids. When platelets were prelabelled with [3H]inositol stimulation with U46619 of control platelets that had not been incubated with EPA significantly increased the labelling of mos1tol phosphates. The increases in inositol phosphate labelling due to U46619 at 10 and 60 s were partially inhibited by premcubat10n of the platelets with 50 μM EPA. Since the activity of cyclo-oxygenase was blocked with aspirin, inhibition of inositol phosphate labelling in response to U46619 indicates either that there may be inhibition of signal transduction without a detectable change in the amount of EPA in platelet phospholipids, that changes in signal transduction require only minute changes in the fatty acid composition of membrane phospholipids, or that after a 1 h incubation with EPA, activation of phospholipase C is affected by a mechanism that is not directly related to incorporation of EPA.

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ANG II AT2 receptor modulates AT1receptor-mediated descending vasa recta endothelial Ca2+ signaling

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00317.2002 ◽

2003 ◽

Vol 284 (3) ◽

pp. H779-H789 ◽

Cited By ~ 23

Author(s):

Kristie Rhinehart ◽

Corey A. Handelsman ◽

Erik P. Silldorff ◽

Thomas L. Pallone

Keyword(s):

Receptor Agonist ◽

Calcium Concentration ◽

Cyclopiazonic Acid ◽

Receptor Activation ◽

Receptor Subtype ◽

Ang Ii ◽

Receptor Stimulation ◽

Vasa Recta ◽

Stimulation Of

We tested whether the respective angiotensin type 1 (AT1) and 2 (AT2) receptor subtype antagonists losartan and PD-123319 could block the descending vasa recta (DVR) endothelial intracellular calcium concentration ([Ca2+]i) suppression induced by ANG II. ANG II partially reversed the increase in [Ca2+]igenerated by cyclopiazonic acid (CPA; 10−5 M), acetylcholine (ACh; 10−5 M), or bradykinin (BK; 10−7 M). Losartan (10−5 M) blocked that effect. When vessels were treated with ANG II before stimulation with BK and ACh, concomitant AT2 receptor blockade with PD-123319 (10−8 M) augmented the suppression of endothelial [Ca2+]i responses. Similarly, preactivation with the AT2 receptor agonist CGP-42112A (10−8 M) prevented AT1 receptor stimulation with ANG II + PD-123319 from suppressing endothelial [Ca2+]i. In contrast to endothelial [Ca2+]i suppression by ANG II, pericyte [Ca2+]i exhibited typical peak and plateau [Ca2+]i responses that were blocked by losartan but not PD-123319. DVR vasoconstriction by ANG II was augmented when AT2 receptors were blocked with PD-123319. Similarly, AT2 receptor stimulation with CGP-42112A delayed the onset of ANG II-induced constriction. PD-123319 alone (10−5 M) showed no AT1-like action to constrict microperfused DVR or increase pericyte [Ca2+]i. We conclude that ANG II suppression of endothelial [Ca2+]i and stimulation of pericyte [Ca2+]i is mediated by AT1 or AT1-like receptors. Furthermore, AT2 receptor activation opposes ANG II-induced endothelial [Ca2+]i suppression and abrogates ANG II-induced DVR vasoconstriction.

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Importance and prospects for design of selective muscarinic agonists

Physiological Research ◽

10.33549/physiolres.931449 ◽

2008 ◽

pp. S39-S47

Author(s):

J Jakubík ◽

P Michal ◽

E Machová ◽

V Doležal

Keyword(s):

Binding Sites ◽

Natural Aging ◽

Receptor Activation ◽

Receptor Subtypes ◽

Muscarinic Agonists ◽

Amyloidogenic Processing ◽

M1 Receptor ◽

The Central Nervous System ◽

M1 Agonist ◽

Stimulation Of

There are five subtypes of muscarinic receptors that serve various important physiological functions in the central nervous system and the periphery. Mental functions like attention, learning, and memory are attributed to the muscarinic M1 subtype. These functions decline during natural aging and an early deficit is typical for Alzheimer s disease. In addition, stimulation of the M1 receptor increases non-amyloidogenic processing of the amyloid precursor protein and thus prevents accumulation of noxious beta-amyloid fragments. The selectivity of classical muscarinic agonists among receptor subtypes is very low due to the highly conserved nature of the orthosteric binding site among receptor subtypes. Herein we summarize some recent studies with the functionally-selective M1 agonist xanomeline that indicate complex pharmacological profile of this drug that includes interactions with and activation of receptor from both orthosteric and ectopic binding sites, and the time-dependent changes of ligand binding and receptor activation. These findings point to potential profitability of exploitation of ectopic ligands in the search for truly selective muscarinic receptor agonists.

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M4 Muscarinic Receptor Activation Modulates Calcium Channel Currents in Rat Intracardiac Neurons

Journal of Neurophysiology ◽

10.1152/jn.1997.78.4.1903 ◽

1997 ◽

Vol 78 (4) ◽

pp. 1903-1912 ◽

Cited By ~ 27

Author(s):

J. Cuevas ◽

D. J. Adams

Keyword(s):

Calcium Channel ◽

Muscarinic Receptor ◽

High Voltage ◽

Receptor Activation ◽

Muscarinic Agonist ◽

Muscarinic Agonists ◽

Maximal Inhibition ◽

Cell Recording ◽

Channel Currents ◽

Intracardiac Neurons

Cuevas, J. and Adams, D. J. M4 muscarinic receptor activation modulates calcium channel currents in rat intracardiac neurons. J. Neurophysiol. 78: 1903–1912, 1997. Modulation of high-voltage–activated Ca2+ channels by muscarinic receptor agonists was investigated in isolated parasympathetic neurons of neonatal rat intracardiac ganglia using the amphotericin B perforated-patch whole cell recording configuration of the patch-clamp technique. Focal application of the muscarinic agonists acetylcholine (ACh), muscarine, and oxotremorine-M to the voltage-clamped soma membrane reversibly depressed peak Ca2+ channel current amplitude. The dose-reponse relationship obtained for ACh-induced inhibition of Ba2+ current ( I Ba) exhibited a half-maximal inhibition at 6 nM. Maximal inhibition of I Ba amplitude obtained with 100 μM ACh was ∼75% compared with control at +10 mV. Muscarinic agonist-induced attenuation of Ca2+ channel currents was inhibited by the muscarinic receptor antagonists pirenzepine (≤300 nM) and m4-toxin (≤100 nM), but not by AF-DX 116 (300 nM) or m1-toxin (60 nM). The dose-response relationship obtained for antagonism of muscarine-induced inhibition of I Ba by m4-toxin gave an IC50 of 11 nM. These results suggest that muscarinic agonist-induced inhibition of high-voltage–activated Ca2+ channels in rat intracardiac neurons is mediated by the M4 muscarinic receptor. M4 receptor activation shifted the voltage dependence and depressed maximal activation of Ca2+ channels but had no effect on the steady-state inactivation of Ca2+ channels. Peak Ca2+ channel tail current amplitude was reduced ≥30% at +90 mV in the presence of ACh, indicating a voltage-independent component to the muscarinicreceptor-mediated inhibition. Both dihydropyridine- and ω-conotoxin GVIA–sensitive and -insensitive Ca2+ channels were inhibited by ACh, suggesting that the M4 muscarinic receptor is coupled to multiple Ca2+ channel subtypes in these neurons. Inhibition of I Ba amplitude by muscarinic agonists was also observed after cell dialysis using the conventional whole cell recording configuration. However, internal perfusion of the cell with 100 μM guanosine 5′-O-(2-thiodiphosphate) trilithium salt (GDP-β-S) or incubation of the neurons in Pertussis toxin (PTX) abolished the modulation of I Ba by muscarinic receptor agonists, suggesting the involvement of a PTX-sensitive G-protein in the signal transduction pathway. Given that ACh is the principal neurotransmitter mediating vagal innervation of the heart, the presence of this inhibitory mechanism in postganglionic intracardiac neurons suggests that it may serve for negative feedback regulation.

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P2Y2 receptor-stimulated phosphoinositide hydrolysis and Ca2+ mobilization in tracheal epithelial cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.2000.279.2.l235 ◽

2000 ◽

Vol 279 (2) ◽

pp. L235-L241 ◽

Cited By ~ 2

Author(s):

Chuen-Mao Yang ◽

Wen-Bin Wu ◽

Shiow-Lin Pan ◽

Yih-Jeng Tsai ◽

Chi-Tso Chiu ◽

...

Keyword(s):

Epithelial Cells ◽

Inositol Phosphate ◽

Extracellular Nucleotides ◽

Receptor Subtype ◽

Secretory Function ◽

P2y2 Receptor ◽

Tracheal Epithelial Cells ◽

Tracheal Epithelial ◽

Selective Agonists ◽

Stimulation Of

Extracellular nucleotides have been implicated in the regulation of secretory function through the activation of P2 receptors in the epithelial tissues, including tracheal epithelial cells (TECs). In this study, experiments were conducted to characterize the P2 receptor subtype on canine TECs responsible for stimulating inositol phosphate (Ins P x) accumulation and Ca2+ mobilization using a range of nucleotides. The nucleotides ATP and UTP caused a concentration-dependent increase in [3H]Ins P xaccumulation and Ca2+ mobilization with comparable kinetics and similar potency. The selective agonists for P1, P2X, and P2Y1 receptors, N 6-cyclopentyladenosine and AMP, α,β-methylene-ATP and β,γ-methylene-ATP, and 2-methylthio-ATP, respectively, had little effect on these responses. Stimulation of TECs with maximally effective concentrations of ATP and UTP showed no additive effect on [3H]Ins P xaccumulation. The response of a maximally effective concentration of either ATP or UTP was additive to the response evoked by bradykinin. Furthermore, ATP and UTP induced a cross-desensitization in [3H]Ins P x accumulation and Ca2+ mobilization. These results suggest that ATP and UTP directly stimulate phospholipase C-mediated [3H]Ins P x accumulation and Ca2+ mobilization in canine TECs. P2Y2receptors may be predominantly mediating [3H]Ins P x accumulation, and, subsequently, inositol 1,4,5-trisphosphate-induced Ca2+mobilization may function as the transducing mechanism for ATP-modulated secretory function of tracheal epithelium.

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Effects of pertussis toxin on growth factor-stimulated inositol phosphate formation and DNA synthesis in Swiss 3T3 cells

Biochemical Journal ◽

10.1042/bj2490917 ◽

1988 ◽

Vol 249 (3) ◽

pp. 917-920 ◽

Cited By ~ 38

Author(s):

C W Taylor ◽

D M Blakeley ◽

A N Corps ◽

M J Berridge ◽

K D Brown

Keyword(s):

Growth Factor ◽

Dna Synthesis ◽

Pertussis Toxin ◽

Inositol Phosphates ◽

Inositol Phosphate ◽

Phosphoinositide Hydrolysis ◽

Polypeptide Growth Factors ◽

Swiss 3T3 ◽

Swiss 3T3 Cell ◽

Stimulation Of

We have compared the effects of pretreatment of Swiss 3T3 cell with pertussis toxin on the stimulation of DNA synthesis and phosphoinositide hydrolysis in response to a wide variety of mitogens. The toxin substantially inhibited the stimulation of DNA synthesis in response to a phorbol ester or various peptide and polypeptide growth factors irrespective of their ability to activate phosphoinositidase C. Production of inositol phosphates in response to platelet-derived growth factor, fibroblast growth factor and prostaglandin F2 alpha were unaffected by the toxin while bombesin- and vasopressin-stimulated formation of inositol phosphates were inhibited by only 27 and 23% respectively. These results argue against a major role for a pertussis toxin-sensitive G protein in coupling any of these mitogen receptors to activation of a phosphoinositidase C. Furthermore, the results suggest that the widespread inhibitory effects of pertussis toxin on mitogen-stimulated DNA synthesis may be unrelated to the toxin's limited actions on phosphoinositide hydrolysis.

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