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

1. Astrocytes from the dorsal spinal cord express P2-purinoceptors which, when stimulated, produce a rise in the intracellular level of free Ca2+ ([Ca2+]i). Previously we have found that the P2Y class of receptor is expressed by nearly all astrocytes from the dorsal horn. To determine whether other metabotropic P2-purinoceptor classes are also present, in this study we investigated the effects of UTP. 2. Application of UTP (1-500 microM, 5-20 s) produced a transient rise in [Ca2+]i in a subpopulation of astrocytes. The magnitude of the peak increase in [Ca2+]i was dependent upon UTP concentration and the EC50 was found to be 5.2 +/- 0.2 microM. Ca2+ responses were maximum at 100 microM UTP. 3. The rise in [Ca2+]i in response to UTP was not affected by removal of extracellular Ca2+. On the other hand, application of the sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase inhibitor, thapsigargin, abolished responses to UTP. These findings indicate that UTP stimulates the release of Ca2+ from a thapsigargin-sensitive intracellular pool. 4. The Ca2+ response to UTP was unaffected by treatment with pertussis toxin, suggesting that UTP responses may be mediated via a pertussis toxin-insensitive G protein. 5. While all cells tested (n = 52) responded to the P2Y-purinoceptor agonist, 2-methylthio-ATP, only a subpopulation of astrocytes (n = 67/93) was responsive to UTP. The presence of UTP-sensitive and UTP-insensitive cells requires the existence of two discrete types of receptor. One receptor, expressed by UTP-insensitive cells, appears to be activated selectively by 2-methylthio-ATP. 6. To investigate whether UTP and 2-methylthio-ATP activate a common type of receptor in UTP-responsive cells, a cross-desensitization strategy was used. Desensitization with prolonged exposure to a high concentration of 2-methylthio-ATP failed to affect responses to UTP and vice versa, indicating that receptors activated by UTP are distinct from those activated by 2-methylthio-ATP. 7. The P2-purinoceptor antagonist, suramin (100 microM), blocked Ca2+ responses to UTP and to 2-methylthio-ATP. 8. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), has been reported to block responses mediated by P2X- and P2Y-purinoceptors in other systems and therefore we investigated its effects on responses to 2-methylthio-ATP and to UTP. PPADS was found to block Ca2+ responses to 2-methylthio-ATP in a concentration-dependent manner with an IC50 of 0.92 +/- 0.1 microM. PPADS also blocked UTP-evoked responses and the IC50 was 7.2 +/- 1.9 microM. At a concentration of 10 microM, PPADS produced a rightward shift in the dose-response curve for UTP and did not affect the maximum response. 9. Calcium responses evoked by the muscarinic agonist, carbachol, were unaffected either by suramin (100 microM) or by PPADS (50 microM). 10. The present results indicate the presence of a novel class of metabotropic P2U-purinoceptor in dorsal spinal astrocytes. In contrast to P2Y-purinoceptors, the P2U-purinoceptor is expressed only by a subpopulation of astrocytes and its sensitivity to suramin and PPADS distinguish this receptor from P2U-purinoceptors found in other tissues.
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PMID:A novel P2-purinoceptor expressed by a subpopulation of astrocytes from the dorsal spinal cord of the rat. 868 Jul 24

ATP-induced phosphoinositide (PI) hydrolysis was studied in cultured astrocytes. To characterize the P2 purinergic receptor-mediated effects of ATP, the subtype-specific agonists 2-methylthio ATP (2-MeSATP), UTP, and alpha, beta-methylene ATP were compared. ATP, UTP, or 2-MeSATP induced a dose-dependent increase of inositol phosphates (IP) accumulation; alpha, beta-methylene ATP and adenosine had no effect. The order of potency was ATP > or = UTP >> 2-MeSATP. Cross-desensitization experiments indicated that ATP interacted with both P2U and P2Y receptors. P2U was the predominant P2 receptor in mediating PI hydrolysis in astrocytes. The effect of ATP, UTP, or 2-MeSATP was markedly inhibited by pretreatment of cells with pertussis toxin (PTX), indicating that both P2U and P2Y receptors coupled to phospholipase C through PTX-sensitive G protein. Short-term (10 min) treatment of cells with 1 microM TPA attenuated ATP, UTP, and 2-MeSATP-induced PI breakdown; however, long-term (24 h) pretreatment resulted in marked potentiation of both ATP and UTP, and restoration of 2-MeSATP responses. In a further analysis of the effect of TPA, 10 min and 1.5 h pretreatment attenuated ATP-and UTP-induced PI breakdown, but this inhibitory action was lost after 3 h of treatment. Both 6 and 24 h pretreatments resulted in a potentiation. Western blot analysis showed translocation of protein kinase C (PKC) alpha, -delta, and -theta from the cytosol to the membrane following 10 min and 1.5 h treatments, and restoration to basal levels in the membrane fraction was seen after 3 h of treatment. On the other hand, partial and complete down-regulation of these three isoforms was seen after 6 and 24 h of treatment, respectively. PKC eta was translocated but not down-regulated by TPA. These results suggested that PKC alpha, -delta, and -theta, not -eta may exert tonic inhibition on P2U receptor-mediated PI turnover in unstimulated astrocytes.
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PMID:ATP-evoked inositol phosphates formation through activation of P2U purinergic receptors in cultured astrocytes: regulation by PKC subtypes alpha, delta, and theta. 872 43

1. We have examined the effects of various purine and pyrimidine nucleotides upon cells cultured from guinea-pig cardiac endothelium (CEC), and find the P2Y-agonist 2-methylthioadenosine triphosphate (2MeSATP) to be a potent (EC50 = 85 +/- 10.2 nM) stimulator of increase in intracellular calcium concentrations, while uridine 5'-triphosphate (UTP) and adenosine 5'-triphosphate (ATP) are less potent but equipotent with one another (EC50s = 2.1 +/- 0.3 and 1.8 +/- 0.2 microM, respectively). 2. While the P2Y receptor exhibited rapid homologous desensitization, this had no effect upon subsequent responsiveness of CEC to either ATP or UTP. Effects of maximal concentrations of ATP and UTP were not only additive, but did not cross-desensitize. Responses to UTP (but not to ATP or 2MeSATP) were blocked by treatment with pertussis toxin (PTX); all three nucleotides appeared to liberate calcium from an intracellular pool. 3. Suramin (30 microM) significantly (P < 0.05) increased the EC50 for ATP-dependent increases in intracellular calcium (5.3 +/- 2.2 microM vs. 2.0 +/- 0.9 microM in the absence of suramin), while it completely blocked the response to 2MeSATP. Suramin had no effect upon responses to UTP at concentrations of 100 microM. 4. We conclude that in addition to the P2Y and P2U subtypes of the ATP receptor, an additional receptor responsive to UTP but exhibiting no affinity for purine nucleotides is present in CEC; this "pyrimidine receptor' liberates intracellular calcium via a G-protein, and may partly mediate the contractile response to UTP in the coronary vasculature.
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PMID:Evidence for a discrete UTP receptor in cardiac endothelial cells. 873 Jul 56

1. The relationship between the stimulation of ATP receptors, the increase in intracellular free calcium concentration ([Ca2+]i; measured using the fluorescent indicator fura-2), contraction and the subtypes of purinoceptors involved were investigated in the small mesenteric artery of the rat. 2. In normal physiological solution, ATP (0.001-3 mM) caused concentration-dependent increases in both [Ca2+]i and contraction. Both responses produced by ATP (1 mM) were inhibited by 50% in the presence of nitrendipine (1 microM) and were abolished in the presence of nitrendipine plus SK&F 96365 (30 microM). 3. In Ca(2+)-free medium, ATP (3 mM) elicited a transient increase in both [Ca2+]i and tension which were abolished by caffeine and decreased by 65% by thapsigargin (1 microM). Moreover, ATP (1 and 3 mM) produced increases in the [3H]D-myo-inositol 1,4,5-trisphosphate ([3H]IP3) content of vessels in a concentration-dependent manner. 4. Treatment of the vessels with Bordetella pertussis toxin (PTX) inhibited contractions to ATP linked to the influx of calcium through nitrendipine-sensitive mechanisms, but not those linked to the release of Ca2+ from intracellular stores nor the capacity of ATP in increasing IP3 content of the vessels. 5. The order of potency of ATP and its analogues in eliciting contraction was alpha, beta-methylene-ATP (alpha, beta-MeATP) > 2-methylthio-ATP (2-MeSATP) > ATP = ADP. The response to ATP was inhibited by suramin. Reactive Blue 2 (up to 100 microM) did not affect the contractile response to ATP. Pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid 4-sodium (PPADS) and alpha, beta-MeATP abolished the response to low concentrations of ATP and reduced contractions elicited by high concentrations of ATP. 6. After blockade of P2X-purinoceptors with PPADS, the order of potency of ATP and its analogues was 2-MeSATP > ATP = ADP. UTP produced concentration-dependent contractions which were not affected by suramin, Reactive Blue 2, PPADS or alpha, beta-MeATP, suggesting the presence of P2U-purinoceptors. 7. The results suggest that low concentrations of ATP activate P2X-purinoceptors and produce an influx of calcium through both voltage-dependent calcium channels sensitive to nitrendipine and through receptor-operated calcium channels sensitive to SK&F 96365. High concentrations of ATP activate P2Y-purinoceptors which promote firstly a nitrendipine-sensitive calcium influx via a PTX-sensitive G protein and secondly a release of Ca2+ from an internal source via the production of IP3.
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PMID:Calcium handling and purinoceptor subtypes involved in ATP-induced contraction in rat small mesenteric arteries. 873 82

Extracellularly applied ATP, UTP and UDP induce a transient increase in the intracellular Ca2+ concentration of mammary cells via a P2U receptor. The P2U receptor in the mammary tumor cell line MMT060562 was cloned and expressed in the human leukemia cell line K-562. The deduced amino acid sequence of the mammary tumor cell P2U receptor was 98% homologous with that of mouse NG108-15 cells. It was a member of the superfamily of GTP-binding-protein-coupled receptors. ATP and UTP induced the increase in the intracellular concentrations of Ca2+ and inositol-1,4,5-trisphosphate in both mammary tumor cells and P2U-receptor-expressed K562 cells. Dose-response curves on the production of inositol-1,4,5-trisphosphate and Ca2+ by ATP and UTP were consistently similar. Injection of GTP enhanced the ATP-induced outward current and injection of GTP gamma S induced a repetitive outward current. Both pertussis and cholera toxins did not affect ATP-induced calcium increase. It was suggested that the P2U receptor coupled with pertussis- and cholera-toxin-insensitive GTP-binding proteins and activated phosphoinositide turnover.
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PMID:Expression cloning and signal transduction pathway of P2U receptor in mammary tumor cells. 873 19

1. HL-60 human leukemia cells are a widely employed model system for the analysis of signal transduction processes mediated via regulatory heterotrimeric guanine nucleotide-binding proteins (G-proteins). HL-60 promyelocytes are pluripotent and can be differentiated into neutrophilic or monocytic cells. 2. HL-60 cells express formyl peptide-, complement C5a-, leukotriene B4 (LTB4)- and platelet-activating factor receptors, receptors for purine and pyrimidine nucleotides, histamine H1- and H2-receptors, beta 2-adrenoceptors and prostaglandin receptors. 3. The major G-proteins in HL-60 cells are pertussis toxin (PTX)-sensitive Gi-proteins (Gi2 > Gi3). Gs-proteins and G-proteins of the Gq-family (e.g., G16) are expressed, too. 4. G-protein-regulated effector systems in HL-60 cells are adenylyl cyclase and phospholipase C-beta 2 (PLC-beta 2) and, possibly, phospholipase D (PLD), nonselective cation (NSC) channels and NADPH oxidase. 5. The expression of signal transduction pathways in HL-60 cells strongly depends on the differentiation state of cells. 6. Formyl peptides, via Gi-proteins, mediate activation of PLC, PLD, NSC channels, NADPH oxidase and azurophilic granule release and are referred to as full secretagogues. In dibutyryl cAMP (Bt2cAMP)-differentiated HL-60 cells, C5a and LTB4 are partial and incomplete secretagogues, respectively. There are substantial differences in the Gi-protein activations induced by formyl peptides, C5a and LTB4. 7. In HL-60 promyelocytes, purine and pyrimidine nucleotides mediate activation of PLC and NSC channels largely via PTX-insensitive G-proteins and induce functional differentiation. In Bt2cAMP-differentiated HL-60 cells, they additionally activate PLD, NADPH oxidase and granule release via PTX-sensitive and -insensitive pathways. ATP and UTP are partial secretagogues. Multiple types of receptors (i.e., P2Y- and P2U-receptors and pyrimidinocyeptors) may mediate the effects of nucleotides in HL-60 cells. 8. Bt2cAMP- and 1 alpha,25-dihydroxycholecalciferol-differentiated HL-60 cells express H1-receptors coupled to Gi-proteins and PTX-insensitive G-proteins. In the former cells, histamine mediates activation of PLC and NSC channels, and in the latter, activation of NSC channels. Histamine is an incomplete secretagogue in these cells. 9. HL-60 promyelocytes express H2-receptors coupled to adenylyl cyclase, PLC, and NSC channels. There are substantial differences in the agonist/antagonist profiles of H2-receptor-mediated cAMP formation and rises in cytosolic Ca2+ concentration, indicative of the involvement of different H2-receptor subtypes. H2-receptors mediate functional differentiation of HL-60 cells. 10. Certain cationic-amphiphilic histamine receptor ligands (i.e., 2-substituted histamines, lipophilic guanidines, and a histamine trifluoromethyl-toluidide derivative) show stimulatory effects in HL-60 cells that are attributable to receptor-independent activation of Gi-proteins.
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PMID:G-protein-coupled receptors in HL-60 human leukemia cells. 874 93

In this study, we have demonstrated that P2-purinoreceptor agonists evoke oscillatory intracellular calcium ([Ca2+]i) responses in human granulosa-lutein cells (GLCs). Intracellular calcium was measured using microspectrofluorimetric techniques. ATP at concentrations of 1-100 microM increased [Ca2+]i, whereas neither adenosine nor AMP evoked changes in [Ca2+]i. The nonhydrolysable ATP analogue, ATP gamma S, also elevated [Ca2+]i with an efficacy similar to that of ATP, indicating that the changes in Ca2+ were not due to ATP hydrolysis, but that human GLCs possess functional P2-purinoreceptors. Uridine triphosphate (UTP) was equipotent to ATP at stimulating [Ca2+]i, and both ATP and UTP were consistently more effective at eliciting a response than ADP, suggesting that human GLCs possess the P2U class of purinergic receptors (ATP = UTP > > ADP > > AMP = adenosine). We have demonstrated that the purinergic agonist-induced changes in [Ca2+]i involve both Ca2+ influx and Ca2+ mobilization from cytosolic stores. Prolonged ATP treatment in Ca(2+)-free buffer (1 mM EGTA) still evokes transient oscillatory changes in [Ca2+]i in a pertussis toxin-insensitive manner. In Ca(2+)-containing conditions, the sustained phase of the response was generally unaffected by verapamil (10 microM), suggesting that influx is not occurring through voltage-dependent Ca(2+)-channels. These findings are consistent with the hypothesis that ATP and other P2-purinergic receptor agonists elicit changes in [Ca2+]i in human ovarian cells and that these events are initiated by the release of Ca2+ from cytosolic stores, and sustained by extracellular calcium ([Ca2+]e) influx. This is the first time that oscillatory patterns of [Ca2+]i have been reported in human GLCs.
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PMID:P2-purinoreceptor evoked changes in intracellular calcium oscillations in single isolated human granulosa-lutein cells. 875 43

Exogenous ATP-induced transient outward currents (IATP) were investigated in isolated adult rat hepatocytes using conventional whole cell patch and nystatin perforated patch recording modes. The IATP increased in a sigmoidal fashion with an increase in ATP concentration, where the half-maximal concentration was 1.4 microM. The order of current potency was 2-methylthio-ATP > or = UTP = ATP > > alpha, beta-methylene-ATP. IATP was depressed in a concentration-dependent manner by suramin and apamin. IATP reversed its direction at the K+ equilibrium potential. IATP occurred easily in hepatocytes obtained from female rats weighing > 250 g. Removal of extracellular Ca2+ had no effect on the peak amplitude of IATP, but thapsigargin abolished it. Intracellular perfusion with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, heparin, guanosine 5'-O-(3-thiotriphosphate), or neomycin also abolished IATP. Pretreatment with pertussis toxin or calmodulin antagonists had no effect on IATP. It was concluded that ATP binding to both P2Y and P2U purinoceptors coupled to G protein may raise apaminsensitive Ca(2+)-dependent K+ conductance via a phospholipase C-inositol trisphosphate-Ca2+ signaling pathway.
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PMID:ATP-induced rise in apamin-sensitive Ca(2+)-dependent K+ conductance in adult rat hepatocytes. 877 73

The effect of Gi coupled receptor activation (adenosine A1 and 5-HT1B receptors) on cholecystokinin receptor-stimulated inositol phosphate accumulation has been investigated in Chinese hamster ovary cells transfected with the human adenosine A1 receptor cDNA (CHO-A1). CHO cells constitutively express the 5-HT1B receptor [Berg, Clarke, Sailstad, Saltzman and Maayani (1994) Mol. Pharmacol. 46, 477-484]. Our previous studies using CHO-A1 cells have revealed that both the adenosine A1 and 5-HT1B receptor are negatively coupled to adenylyl cyclase activity and stimulate increases in [Ca2+]i, through a pertussis toxin-sensitive pathway. In the present study the selective adenosine A1 receptor agonist N6-cyclopentyladenosine stimulated a pertussis toxin-sensitive increase in total [3H]inositol phosphate accumulation. The sulphated C-terminal octapeptide of cholecystokinin (CCK-8) stimulated a robust and pertussis toxin-insensitive increase in [3H]inositol phosphate accumulation through the activation of CCKA receptors. Co-stimulation of CHO-A1 cells with N6-cyclopentyladenosine and CCK-8 produced a synergistic increase in [3H]inositol phosphate accumulation. The synergistic interaction between N6-cyclopentyladenosine and CCK-8 was abolished in pertussis toxin-treated cells. Synergy between N6-cyclopentyladenosine and CCK-8 still occurred in the absence of extracellular calcium. The 5-HT1B receptor agonist 5-carboxyamidotryptamine did not stimulate a measurable increase in [3H]inositol phosphate accumulation. Furthermore, 5-carboxyamidotryptamine had no significant effect on CCK-8 mediated [3H]inositol phosphate production. Activation of endogenous P2U receptors (Gq/Gll coupled) with ATP gamma S produced a significant increase in [3H]inositol phosphate accumulation. Co-stimulation of CHO-A1 cells with ATP gamma S and CCK-8 produced additive increases in [3H]inositol phosphate accumulation. These data indicate that CHO-A1 cells may prove a useful model system in which to investigate further the mechanisms underlying the intracellular 'cross-talk' between phospholipase C coupled receptors (Gq/Gll linked) and Gi/Go coupled receptors.
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PMID:Synergistic interactions between human transfected adenosine A1 receptors and endogenous cholecystokinin receptors in CHO cells. 879 Oct 2

1. The effects of extracellular adenosine 5'-triphosphate (ATP) on smooth muscles are mediated by a variety of purinoceptors. In this study we addressed the identity of the purinoceptors on smooth muscle cells (SMC) cultured from human large coronary arteries. Purinoceptor-mediated increases in [Ca2+]i were measured in single fura-2 loaded cells by applying a digital imaging technique, and the formation of inositol phosphate compounds was quantified after separation on an anion exchange column. 2. Stimulation of the human coronary artery SMC (HCASMC) with extracellular ATP at concentrations of 0.1-100 microM induced a transient increase in [Ca2+]i from a resting level of 49 +/- 21 nM to a maximum of 436 +/- 19 nM. The effect was dose-dependent with an EC50 value for ATP of 2.2 microM. 3. The rise in [Ca2+]i was independent of the presence of external Ca2+, but was abolished after depletion of intracellular stores by incubation with 100 nM thapsigargin. 4. [Ca2+]i was measured upon stimulation of the cells with 0.1-100 microM of the more specific P2-purinoceptor agonists alpha, beta-methyleneadenosine 5'-triphosphate (alpha,beta-MeATP), 2-methylthioadenosine 5'-triphosphate (2MeSATP) and uridine 5'-triphosphate (UTP). alpha, beta-MeATP was without effect, whereas 2MeSATP and UTP induced release of Ca2+ from internal stores with 2MeSATP being the most potent agonist (EC50 = 0.17 microM), and UTP having a potency similar to ATP. The P1 purinoceptor agonist adenosine (100 microM) did not induce any changes in [Ca2+]i. 5. Stimulation with a submaximal concentration of UTP (10 microM) abolished a subsequent ATP-induced increase in [Ca2+]i, whereas an increase was induced by ATP after stimulation with 10 microM 2MeSATP. 6. The phospholipase C (PLC) inhibitor U73122 (5 microM) abolished the purinoceptor-activated rise in [Ca2+]i, whereas pretreatment with the Gi protein inhibitor pertussis toxin (PTX, 500 ng ml-1) was without effect on ATP-evoked [Ca2+]i increases. 7. Receptor activation with UTP and ATP resulted in formation of inositol phosphates with peak levels of inositol 1, 4, 5-trisphosphate (Ins(1, 4, 5)P3) observed 5-20 s after stimulation. 8. These findings show, that cultured HCASMC express G protein-coupled purinoceptors, which upon stimulation activate PLC to induce enhanced Ins(1, 4, 5)P3 production causing release of Ca2+ from internal stores. Since a release of Ca2+ was induced by 2MeSATP as well as by UTP, the data indicate that P2y- as well as P2U-purinoceptors are expressed by the HCASMC.
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PMID:P2-purinoceptor-mediated formation of inositol phosphates and intracellular Ca2+ transients in human coronary artery smooth muscle cells. 884 27


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