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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pulmonary levels of cGMP and cAMP in mice sensitized to methacholine and histamine with B. pertussis were examined to determine whether sensitization could be the result of an alteration in the metabolism of these cyclic nucleotides. The results presented show that in sensitized mice, methacholine raised cGMP to levels that were about double those produced without sensitization. In analogous experiments, histamine raised cGMP by approximately 100% in sensitized mice without producing significant increases in nonsensitized groups. Atropine completely blocked the cGMP rises produced by methacholine but did not eliminate those produced by histamine, thus indicating that cholinergic, but not the histaminergic elevation of cGMP involves activation of muscarinic receptors. The influence of pertussis on cAMP appeared to be opposite in direction from cGMP, i.e., a small but significant drop in cAMP levels was found following methacholine administration to sensitized, but not to nonsensitized mice. It was concluded that pertussis sensitization increases the responsiveness of the pulmonary guanylate cyclase-cGMP system to methacholine and histamine, and that the altered patterns of cGMP accumulation may contribute to the biochemical mechanism of sensitization.
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PMID:Effects of methacholine, histamine and atropine on pulmonary guanosine-3', 5'-monophosphate levels in hypersensitive mice. 18 63

Sperm-mediated egg activation may be analogous to ligand-mediated signal transduction through G protein-coupled receptors. We investigated this possibility in the mouse egg by microinjecting mouse oocytes with an m1 muscarinic receptor mRNA. Following oocyte maturation in vitro, the metaphase II-arrested eggs were treated with acetylcholine and its effect was examined on zona pellucida modifications and pronuclear formation, which are end points of early and late egg activation, respectively. Treatment of these eggs with acetylcholine reveals that both the ZP2 to ZP2f conversion and pronuclear formation occur. Atropine and microinjected GDP beta S block the acetylcholine-induced ZP2 conversion, suggesting that the acetylcholine effects are mediated via a functional G protein-coupled m1 receptor. The acetylcholine-induced ZP2 conversion, however, is not inhibited by pertussis toxin under conditions in which greater than 90% of the endogenous Gi is inactivated by ADP ribosylation. The presence of a pertussis toxin-insensitive G protein, Gq, is detected by immunoblotting; this G protein could be a candidate to mediate the pertussis toxin-insensitive effects of acetylcholine. Results of these experiments are consistent with the hypothesis that receptor-mediated G protein activation may play a role in egg activation.
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PMID:Role of G proteins in mouse egg activation: stimulatory effects of acetylcholine on the ZP2 to ZP2f conversion and pronuclear formation in eggs expressing a functional m1 muscarinic receptor. 157 93

Muscarinic receptor-linked Ca2+ mobilization and changes in cyclic AMP were studied in SH-SY5Y and IMR 32 human neuroblastoma cell lines. Muscarinic agonists acetylcholine, carbachol, methacholine and muscarine induced an increase in cytosolic free Ca2+ in a pertussis toxin (100 ng/ml)-insensitive manner in both cell lines. The ED50 values in IMR 32 cells (8-98 microM) were one order of magnitude higher than in SH-SY5Y cells (0.3-1.6 microM). Oxotremorine and pilocarpine failed to mobilize Ca2+ in IMR 32 cells. Pirenzepine antagonized carbachol-induced Ca2+ mobilization in SH-SY5Y cells with a Ki value in the range of 150-189 nM whereas the corresponding values in IMR 32 cells were 24-28 nM. Atropine inhibited a carbachol-stimulated increase in cytosolic Ca2+ with an equal potency in both cell lines (Ki 2-3 nM). Carbachol stimulated cyclic AMP (cAMP) accumulation in SH-SY5Y cells in a pertussis toxin-insensitive manner. In IMR 32 cells carbachol inhibited prostaglandin E1-stimulated cAMP accumulation. Treatment of IMR 32 cells with pertussis toxin abolished the inhibition of stimulated cAMP accumulation. These results suggest that in SH-SY5Y cells the M3 muscarinic receptor couples to both Ca2+ mobilization and stimulation of cAMP accumulation. In IMR 32 cells the M1 receptor seems to couple to Ca2+ mobilization whereas the inhibition of stimulated cAMP accumulation is coupled to a non-M1 subtype by an inhibitory G-protein.
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PMID:Differential coupling of muscarinic receptors to Ca2+ mobilization and cyclic AMP in SH-SY5Y and IMR 32 neuroblastoma cells. 165 23

1. The effects of activation of muscarinic receptors on the voltage-dependent calcium current, ICa, in parasympathetic neurones were examined. 2. Neurones were enzymatically isolated from the interatrial septum of bull-frog (Rana catesbeiana) heart, and were maintained in short-term (1-6 day) tissue culture. ICa was recorded from the cells using whole-cell patch-clamp methods (Clark, Tse & Giles, 1990). 3. External application of 2 nM to 10 microM acetylcholine (ACh) reduced the amplitude and slowed the time course of activation of ICa. These effects were dependent on membrane potential; they were most pronounced at potentials near the peak of the current-voltage relation for ICa (i.e. +10 to +15 mV), whereas at more-negative potentials (i.e. -15 to -25 mV) the effects on both amplitude and time course were relatively small. 4. Atropine (1 microM) completely blocked the action of 1 microM-ACh, indicating that the effects of ACh on ICa were mediated by activation of muscarinic receptors. 5. Other muscarinic agonists, such as carbamylcholine (0.1-10 microM), DL-muscarine (0.1-2.5 microM) and oxotremorine (5 microM), had similar effects on ICa to ACh. 6. A guanine nucleotide-binding protein (G-protein) is involved in this muscarinic inhibition of ICa. Inclusion of the non-hydrolysable guanosine triphosphate analogue guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S; 200 microM) in the intracellular solutions mimicked the effects of ACh, and application of external ACh in the presence of internal GTP-gamma-S produced smaller changes in ICa than in control conditions. Inclusion of another non-hydrolysable analogue, guanosine 5'-O-(2-thiodiphosphate) (GDP-beta-S; 0.5-5 mM), blocked the inhibitory effect of ACh on ICa. 7. The G-protein involved in the inhibition of ICa was sensitive to pertussis toxin (islet-activating protein; IAP). The inhibition of ICa by carbamylcholine (5 microM) was reduced by about 90% after incubating cells for 12-15 h in culture medium containing 200 ng/ml IAP. 8. The possible roles of cyclic AMP or cyclic GMP-dependent protein kinases, or protein kinase C, in the muscarinic inhibition of ICa were tested, but these enzymes appear not to be directly involved.
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PMID:Muscarinic modulation of calcium current in neurones from the interatrial septum of bull-frog heart. 217 Jun 34

Cholinergic agents decrease myocardial contractility in part by inhibiting adenylate cyclase (EC 4.6.1.1) activity. We have found that after a prolonged preincubation period (greater than 6 h), washout of cholinergic agents from embryonic chick hearts or cultured heart cells results in a persistent increase in their basal and catecholamine-stimulated cAMP content. Membranes prepared from pretreated cells have elevated basal, forskolin-, and catecholamine-stimulated adenylate cyclase activities. This myocardial adaptation to cholinergic agents is analogous to changes in nerve cells and other cell types after prolonged exposures to narcotics or other inhibitors of adenylate cyclase, respectively. A rapid (less than 5 min) adaptation response to cholinergic agents can also be demonstrated in heart cells by quickly blocking agonist action with atropine. Atropine alone has no effect, but after a brief preincubation period with agonists (methacholine or oxotremorine), the addition of atropine transiently enhances catecholamine-stimulated cAMP accumulation by 2.5-fold. These responses are absent in heart cells pretreated with pertussis toxin. The data indicate that the response is not mediated by the phosphoinositide pathway, which has been demonstrated to be insensitive to pertussis toxin in chick heart. Enhanced cAMP accumulation after termination of muscarinic agonist action may provide an explanation for the observation that acetylcholine sometimes produces biphasic contractile responses.
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PMID:Enhanced cAMP accumulation after termination of cholinergic action in the heart. 244 Jul 52

Carbamoylcholine (carbachol) has been shown to inhibit somatostatin release from gastric D-cells. We observed that this dose-dependent inhibitory effect was accompanied by decreases in cellular cyclic adenosine 3':5'-monophosphate (cAMP) production and increases in parameters of membrane inositol phospholipid turnover. However, after pretreatment of D-cells with pertussis toxin (200 ng/ml), carbachol paradoxically stimulated basal somatostatin release and potentiated the secretagogue action of forskolin. Pertussis toxin pretreatment blocked the ability of carbachol to decrease cAMP production but changes in inositol phospholipid turnover were unaffected. Atropine reversed all of the observed changes induced by carbachol. These data suggest that muscarinic cholinergic receptors mediate both stimulatory and inhibitory regulation of D-cells. The inhibitory effect may involve pertussis toxin-sensitive inhibitory guanine nucleotide binding proteins while the stimulatory effect may result from the consequences of membrane phosphoinositide turnover.
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PMID:Divergent stimulatory and inhibitory actions of carbamoylcholine on gastric D-cells. 288 21

The production of inositol phosphates in response to carbachol was studied in rat anterior pituitary tissue prelabelled with [3H]inositol. Carbachol (10 microM) stimulated inositol mono-, bis- and trisphosphate production (IP1, IP2 and IP3) by 360 +/- 49, 338 +/- 49 and 503 +/- 49 (mean +/- SEM, P less than 0.001) percent respectively during a 30 min incubation. Mean basal production was 5.4 +/- 0.3, 4.1 +/- 0.5 and 0.9 +/- 0.3 expressed as a percent of total [3H]inositol lipid for IP, IP2 and IP3 respectively. Stimulated inositol phosphate production was dose dependent and detectable after 5 min. Atropine prevented this stimulation indicating mediation via muscarinic receptors. Removal of extracellular Ca2+ reduced both basal and stimulated total inositol phosphate production by 60% and 56% respectively but did not impair carbachol-induced phosphoinositide hydrolysis per se. Pretreatment of pituitary tissue with either somatostatin (5 micrograms/ml) or pertussis toxin (1 microgram/ml) had no effect on either basal or stimulated inositol phosphate production. These results demonstrate a cholinergic stimulation of phosphatidylinositol bisphosphate (PIP2) hydrolysis in the anterior pituitary which may be important in the action of cholinergic agonists on pituitary hormone secretion.
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PMID:Cholinergic stimulation of phosphoinositide hydrolysis in rat anterior pituitary. 289 24

The inhibitory pathway of cardiac cAMP-dependent protein kinase regulated Cl- conductance was investigated using the whole-cell configuration of patch-clamp techniques in single guinea pig ventricular myocytes. Pertussis toxin-sensitive G proteins (Gi), mediating the signal transductions between muscarinic receptors and adenylate cyclase, have a substantial tonic activity even in the absence of muscarinic receptor modulators. Muscarinic agonists or antagonists (like atropine) either increase or decrease this basal activity of Gi by altering the proportion of active and inactive forms of the receptors. Similar to L-type Ca-channel currents, the Cl- conductance showed a transient over-recovery upon cessation of brief muscarinic receptor stimulation by carbachol (CCh) (rebound). Atropine alone enhanced the Cl- conductance elicited by low concentrations of Iso (reverse agonist). After washout of atropine, the over-suppression of the conductance was observed as a mirror image of CCh-induced rebound (reverse rebound). Both types of rebound became prominent when cell dialysis with pipette solutions containing 100 microM GTP was minimized with high-resistance pipettes. Endogenous GTP is therefore an intracellular modulator, and not simply a mediator, of Gi-dependent signal transduction.
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PMID:Inhibitory pathway of cardiac PKA-dependent Cl- conductance via pertussis toxin-sensitive G proteins. 775 28

Many important airway epithelial cell functions are regulated by intracellular cAMP. Adenylyl cyclase, the enzyme that synthesizes cAMP, is under dual regulation in many cells, but muscarinic agonists have not been shown to inhibit adenylyl cyclase in human and dog epithelial cells, despite the presence of muscarinic receptors. We question whether the lack of inhibition was related to the absence of a component of the inhibitory pathway or a lack of coupling between the components. The GTP-binding regulatory proteins (G proteins) that regulate adenylyl cyclase activity in airway epithelium have not been well characterized. We used primary cultures of guinea pig tracheal epithelial cells as a model system and identified the G proteins that modulate adenylyl cyclase activity. Immunoblot analysis demonstrated the presence of alpha subunits corresponding to stimulatory (Gs alpha) and inhibitory [Gi alpha (2) and Gi alpha (3)] G proteins as well as beta chains. These G proteins were functionally coupled to stimulation and inhibition of adenylyl cyclase in epithelial membrane preparations. Pertussis toxin-catalyzed [32P]ADP-ribosylation of Gi alpha was significantly reduced by 100 microM GTP gamma S (78.4 +/- 3.6% of control), by 100 mM NaF (41.9 +/- 9.1% of control), and by carbachol (100 microM) (29.2 +/- 9.0% of control). Atropine (10 microM) inhibited the carbachol effect by greater than 90%, suggesting that the muscarinic receptors were functionally coupled to Gi proteins. beta-Adrenergic agonists increased adenylyl cyclase activity, but muscarinic agonists failed to inhibit this enzyme. In summary, guinea pig tracheal epithelial membranes contain muscarinic receptors, Gi alpha (2) and adenylyl cyclase, which are appropriately coupled.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of GTP-binding proteins coupled to inhibition of adenylyl cyclase in guinea pig tracheal epithelial cells. 800 43

We have used a luciferase reporter gene under the transcriptional control of a cAMP response element as a sensitive monitor of the regulation by muscarinic acetylcholine receptors (mAChRs) of intracellular cAMP levels and cAMP-regulated gene expression. Treatment with the muscarinic agonist carbachol results in an increase in luciferase activity in JEG-3 cells transiently transfected with mouse m1 (8-10-fold) and chick m4 (3-5-fold) mAChRs. Control experiments indicate that these responses are not due to a calcium-mediated pathway and are dependent upon a functional protein kinase A. The m1 and m4 responses are not sensitive to pertussus toxin and the m4 response was potentiated by it. Thus, these responses do not result from direct stimulation of adenylate cyclase by beta gamma subunits released from pertussis toxin-sensitive G-proteins. Atropine treatment of cells transfected with high levels of m4 mAChR, but not m1, causes an elevation in basal levels of cAMP response element-mediated luciferase expression in the absence of agonist. This suggests that the m4 receptor is spontaneously active and can cause constitutive inhibition of adenylyl cyclase that is relieved by atropine treatment. Surprisingly, the m4 receptor exhibits little if any agonist-induced inhibition of luciferase expression at either low or high levels of receptor expression. JEG-3 cells express Gi alpha-1 and Gi alpha-3 but not Gi alpha-2. Cotransfection of Gi alpha subunits with m4 demonstrates that the m4 receptor requires Gi alpha-2 for optimal agonist-mediated inhibition. Even in the presence of Gi alpha-2, high levels of receptor increased luciferase expression at high concentrations of agonist. Thus, the m4 mAChR can undergo a switch in functional coupling from inhibition to stimulation of adenylyl cyclase. This switch is dependent on the level of receptor expression, the subtypes of G-proteins coexpressed with the receptor, and the concentration of agonist. Furthermore, we demonstrate that the Gi alpha-2 G-protein alpha subunit preferentially couples the m4 mAChR to inhibition of adenylyl cyclase in JEG-3 cells.
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PMID:Differential regulation of cAMP-mediated gene transcription by m1 and m4 muscarinic acetylcholine receptors. Preferential coupling of m4 receptors to Gi alpha-2. 814 70


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