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)

1. Actions of histamine on the voltage-dependent Ba2+(Ca2+) currents (IBa, ICa) were investigated using the whole-cell patch-clamp technique on dispersed smooth muscle cells from the rabbit saphenous artery. 2. Histamine (half-maximal dose, EC50 = 530 nM) augmented the IBa evoked by a brief depolarizing pulse (100 ms duration; to +10 mV from a holding potential of -80 mV) in a concentration-dependent manner. The maximum augmentation was obtained with 30 microM-histamine (1.29 times control). This augmentation of IBa was inhibited by the H3-antagonist, thioperamide (Ki = 30 nM, slope of the Schild plot = 1.0), but not by H1- or H2-antagonists (mepyramine or diphenhydramine, or cimetidine, respectively). 3. An H3-agonist, R alpha-methylhistamine (EC50 = 93 nM), also augmented IBa in a concentration-dependent manner at a holding potential of -80 mV and the maximum augmentation (1.25 times control) was obtained with 10 microM. This augmentation was also inhibited by thioperamide, but not by the above H1- and H2- antagonists. 4. Intracellularly applied 500 microM-guanosine 5'-triphosphate (GTP) enhanced, but 1 mM-guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) abolished, the histamine-induced augmentation of IBa. When one of the non-hydrolysable GTP analogues, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; greater than 5 microM), guanylyl-imidodiphosphate (GMP-PNP; 200 microM) or guanylyl (beta, gamma-methylene)-diphosphonate (GMP-PCP; 1 mM) was intracellularly applied, the IBa amplitude evoked without the application of histamine was not affected, but the excitatory effect of histamine on IBa was reversed to an inhibition. Pre-treatment with pertussis toxin (PTX: 300 ng/ml and 3 micrograms/ml) did not modify the histamine-induced responses in the absence or presence of GTP gamma S. 5. 4 beta-Phorbol 12,13-dibutylate (PDBu) increased the amplitude of IBa. However, this action of PDBu was not enhanced by the application of GTP (500 microM) in the pipette, but additional application of histamine further increased the amplitude of IBa. Pre-treatment with a potent non-selective protein kinase inhibitor, 1-(5-isoquinolinesulphonyl)-2-methylpiperazine dihydrochloride (H-7; 100 microM), did not modify the histamine-induced current augmentation or inhibition observed in the presence or absence of intracellular GTP gamma S.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Histamine H3-receptor activation augments voltage-dependent Ca2+ current via GTP hydrolysis in rabbit saphenous artery. 131 41

Human polymorphonuclear neutrophils (PMN) respond to ATP with an elevation in intracellular calcium and a marked enhancement of O2-production in response to stimulation by the chemotactic peptide N'-formyl-Met-Leu-Phe (FMLP). These pertussis toxin-sensitive pathways appear to be mediated by a nucleotide receptor(s) on the surface of human PMN. In the current study, we have examined the binding to intact human PMN of the ATP analog, adenosine 5'-O-(3-thio[35S] triphosphate) [( 35S]ATP gamma S). On the basis of Scatchard analysis, the binding of [35S]ATP gamma S involves at least two sites, one of high and one of low affinity. In the presence of sodium thiophosphate, a compound which did not affect intracellular increases in calcium induced by ATP or N'-formyl-Met-Leu-Phe, a significant fraction of the [35S]ATP gamma S binding was eliminated. This reduction involved both high and low affinity binding of [35S]ATP gamma S and was related to a reduction in numbers of binding sites. The Kd values for the high affinity binding site were unaffected by the presence of sodium thiophosphate, although the low affinity Kd values were numerically increased by 2-fold. In the presence of thiophosphate, [35S]ATP gamma S binding was specific, saturable, and reversible, and was related to a single class of high affinity (Kd = 36 +/- 19 nM) binding sites (184 +/- 144 sites/cell), together with a second class of low affinity (Kd = 1110 +/- 503 nM) binding sites (13,562 +/- 6,851 sites/cells). Competitive binding experiments, based on the ability of nucleotides and ATP analogs to block [35S]ATP gamma S binding to PMN, revealed a rank order of ATP gamma S greater than ATP greater than 2-MeS-ATP = 8-Bromo ATP greater than ADP = ITP greater than AMP-PCP = GTP much greater than CTP. A comparison between the ability of nucleotides to compete with [35S]ATP gamma S binding and their ability to induce a biologic response (elevation of intracellular calcium) revealed a close correlation (r2 = 0.83). These findings support the possibility of a common nucleotide PMN receptor functionally linked to a cellular response which involves increases in intracellular calcium.
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PMID:Adenosine-5'-O-(3-thiotriphosphate) binding to human neutrophils. Evidence for a common nucleotide receptor. 165 77

When added to intact C6 glioma cells in the micromolar range of concentrations, ADP and ATP induce an inhibition of the isoproterenol-elicited cAMP responses. ATP is rapidly hydrolyzed by the ectonucleotidases present on these cells, with an apparent Km of 50 microM and a Vmax of 1.1 nmol/min/10(6) cells. cAMP responses are also inhibited by millimolar concentrations of either ATP in the presence of an ATP-regenerating system to prevent ADP accumulation or AMP-PCP. These observations show that, in C6 glioma cells, ADP is a more potent inhibitor of cAMP production than ATP, the latter acting indirectly, via its rapid hydrolysis to ADP. The additive inhibition of isoproterenol-elicited cAMP responses induced, on one hand, by the treatment of the cells with a phorbol ester and by addition of ADP to the cells, and, on the other hand, by the progressive disappearance of the effects of ADP and ATP when cells are treated with increasing concentrations of Pertussis toxin, demonstrate that ADP and ATP exert their action in C6 glioma cells via a P2 purinoceptor probably negatively coupled to adenylate cyclase and a G regulatory protein.
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PMID:ADP and, indirectly, ATP are potent inhibitors of cAMP production in intact isoproterenol-stimulated C6 glioma cells. 255 Dec 69

Glial cells are closely associated with synapses and are modulated by neurotransmitters released during synaptic transmission. At many synapses, ATP is released during synaptic transmission and is involved in cell-cell signaling. Since glial cells have purinoceptors, it is possible that ATP mediates synaptic neuron-glia signaling. This work aims at determining which types of purinoceptors are present on perisynaptic Schwann cells, the perisynaptic glial cells at the frog neuromuscular junction, and test their sensitivity to endogenous purines by monitoring the relative changes of intracellular Ca2+. Local application of ATP induced the release of Ca2+ from internal stores. Adenosine induced Ca2+ responses that were blocked by A1 receptor antagonists and mimicked by an A1 receptor agonist and were caused by the release of Ca2+ from internal stores via a pertussis toxin-sensitive G-protein. A2 receptor antagonists had no effect on Ca2+ responses induced by adenosine. Me-S-ATP, an ATP analog, triggered Ca2+ release from internal stores via a pertussis toxin-sensitive G-protein, consistent with the activation of P2Y receptors. L-AMP-PCP, another ATP analog, induced Ca2+ entry mainly through L-type Ca2+ channels by a pertussis toxin-insensitive mechanism, consistent with the activation of P2X receptors. Blockade of adenosine receptors did not affect glial Ca2+ responses induced by nerve evoked transmitter release. However, blockade of ATP receptors reduced the size and increased the delay of the responses. Hence, purinoceptors are present on the perisynaptic Schwann cells and are activated by endogenous ATP released during synaptic transmission.
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PMID:Purinergic receptors and their activation by endogenous purines at perisynaptic glial cells of the frog neuromuscular junction. 747 66

Under conditions of low intracellular [Mg2+] ([Mg2+]i), achieved by dialysis with pipette solutions containing ethylenediamine tetraacetic acid (EDTA), 1,2-bis(2-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid (BAPTA) and adenosine triphosphate (ATP) as chelator, calcium currents through the L-type calcium channels (ICa) were increased in frog ventricular myocytes. Total suppression of phosphorylation by depleting the cell of ATP with a cocktail of beta, gamma-methyleneadenosine 5'-triphosphate (AMP-PCP) 2-deoxyglucose and carboxylcyanide-M-chlorophenylhydrazone (CCCP) did not inhibit the increase in ICa in the Mg2+-deficient medium. Thus, the involvement of phosphorylation process in the increase in ICa was not likely. Effective suppression of this enhancement of ICa was achieved by the application of guanosine triphosphate (GTP). From the dose-response curve for GTP, the GTP concentration required for half-maximal inhibition (IC50) was estimated to be 4.0 microM at pMg 6. This GTP-induced suppression of ICa is not due to the guanine nucleotide binding protein (G-protein) cascade, because both activators and inhibitors of G-protein, which are structural analogues of GTP, suppressed ICa similarly. Treatment with pertussis toxin (PTX) did not affect the inhibitory action of Mg2+ and GTP on ICa. GTP is therefore assumed to bind directly to the Ca2+ channel. Interaction of Mg2+ and GTP with the Ca2+ channel activated in the Mg2+-deficient medium was examined by comparing the dose/response curves for GTP at two different [Mg2+]. The IC50 for GTP suppression was estimated to be 5.7 microM at pMg 6 and 6.9 microM at pMg 5. The results suggest strongly that Mg2+ and GTP independently bind and control Ca2+ channels.
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PMID:Modulation of Ca2+ channels by intracellular Mg2+ ions and GTP in frog ventricular myocytes. 876 3

The role of nucleoside diphosphate kinase (NDKP), which converts GDP to GTP, in the coupling of mu-opioid receptors to G protein was investigated in membranes of Chinese hamster ovary cells stably transfected with the cloned rat mu-opioid receptor (rmor). Endogenous NDPK activity in membranes was determined to be 0.60+/-0.02 micromol/mg protein/30 min UDP (at 10 mM), a competitive substrate of NDPK for GDP with no effect on guanine nucleotide binding to G proteins, reduced basal [35S]GTPgammaS binding and unmasked morphine-stimulated [35S]GTPgammaS binding to pertussis toxin-sensitive G proteins, indicating that [35S]GTPgammaS binding to NDPK accounts for part of its high basal binding. UDP increased the extent of morphine-induced increase in [35S]GTPgammaS binding in the presence of GDP, most likely by reducing basal binding and inhibiting conversion of GDP to GTP. ATP greatly reduced morphine-induced increase in [35S]GTPgammaS binding, whereas AMP-PCP (adenylyl-(beta,gamma-methylene)-diphosphoate tetralithium salt), which cannot serve as the phosphate donor for NDPK, did not, demonstrating that effects of ATP is mediated by the NDPK product GTP. In addition, GDP and ATP increased the Kd and lowered the Bmax of the agonist [3H]DAMGO ([D-Ala2,N-Me-Phe4,Gly5ol]-Enkephalin) for the mu-opioid receptor and GDP alone increased Kd, most likely through their conversion to GTP by NDPK. Addition of exogenous NDPK enhanced the inhibitory effects of GDP and combined GDP and ATP on [3H]DAMGO binding. Thus, NDPK appears to play a role in modulating signal transduction of and agonist binding to mu-opioid receptors.
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PMID:Nucleoside diphosphate kinase associated with membranes modulates mu-opioid receptor-mediated [35S]GTPgammaS binding and agonist binding to mu-opioid receptor. 1045 35

1. Measurements of cell capacitance were used to investigate the molecular mechanisms by which somatostatin inhibits Ca(2+)-induced exocytosis in single rat glucagon-secreting pancreatic alpha-cells. 2. Somatostatin decreased the exocytotic responses elicited by voltage-clamp depolarisations by 80 % in the presence of cyclic AMP-elevating agents such as isoprenaline and forskolin. Inhibition was time dependent and half-maximal within 22 s. 3. The inhibitory action of somatostatin was concentration dependent with an IC(50) of 68 nM and prevented by pretreatment of the cells with pertussis toxin. The latter effect was mimicked by intracellular dialysis with specific antibodies to G(i1/2) and by antisense oligonucleotides against G proteins of the subtype G(i2). 4. Somatostatin lacked inhibitory action when applied in the absence of forskolin or in the presence of the L-type Ca(2+) channel blocker nifedipine. The size of the omega-conotoxin-sensitive and forskolin-independent component of exocytosis was limited to 60 fF. By contrast, somatostatin abolished L-type Ca(2+) channel-dependent exocytosis in alpha-cells exposed to forskolin. The magnitude of the latter pool amounted to 230 fF. 5. The inhibitory effect of somatostatin on exocytosis was mediated by activation of the serine/threonine protein phosphatase calcineurin and was prevented by pretreatment with cyclosporin A and deltamethrin or intracellularly applied calcineurin autoinhibitory peptide. Experiments using the stable ATP analogue AMP-PCP indicate that somatostatin acts by depriming of granules. 6. We propose that somatostatin receptors associate with L-type Ca(2+) channels and couple to G(i2) proteins leading to a localised activation of calcineurin and depriming of secretory granules situated close to the L-type Ca(2+) channels.
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PMID:Somatostatin inhibits exocytosis in rat pancreatic alpha-cells by G(i2)-dependent activation of calcineurin and depriming of secretory granules. 1153 41