ATP Antagonizes Thrombin-Induced Signal Transduction through 12(S)-HETE and cAMP

In this study we have investigated the role of extracellular ATP on thrombin induced-platelet aggregation (TIPA) in washed human platelets. ATP inhibited TIPA in a dose-dependent manner and this inhibition was abolished by apyrase but not by adenosine deaminase (ADA) and it was reversed by extracellular magnesium. Antagonists of P2Y1 and P2Y12 receptors had no effect on this inhibition suggesting that a P2X receptor controlled ATP-mediated TIPA inhibition. ATP also blocked inositol phosphates (IP1, IP2, IP3) generation and [Ca2+]i mobilization induced by thrombin. Thrombin reduced cAMP levels which were restored in the presence of ATP. SQ-22536, an adenylate cyclase (AC) inhibitor, partially reduced the inhibition exerted by ATP on TIPA. 12-lipoxygenase (12-LO) inhibitors, nordihidroguaretic acid (NDGA) and 15(S)-hydroxy-5,8,11,13- eicosatetraenoic acid (15(S)-HETE), strongly prevented ATP-mediated TIPA inhibition. Additionally, ATP inhibited the increase of 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12(S)-HETE) induced by thrombin. Pretreatment with both SQ- 22536 and NDGA almost completely abolished ATP-mediated TIPA inhibition. Our results describe for the first time that ATP implicates both AC and 12-LO pathways in the inhibition of human platelets aggregation in response to agonists.Fil: Burzaco, Jaione. UNIVERSIDAD DEL PAIS VASCO;Fil: Conde, Manuel. UNIVERSIDAD DEL PAIS VASCO;Fil: Parada, Luis Antonio. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Salta. Instituto de Patologia Experimental;Fil: Zugaza, José L.. UNIVERSIDAD DEL PAIS VASCO;Fil: Dehaye, Jean-Paul. UNIVERSIDAD DEL PAIS VASCO;Fil: Marino, Aída. UNIVERSIDAD DEL PAIS VASCO

Pharmacological evidence for the stimulation of NADPH oxidase by P2X7 receptors in mouse submandibular glands

ATP in the 100 μM-1 mM concentration range provoked a calcium-independent increase of the oxidation of dichlorodihydrofluorescein (DCFH) to dichlorofluorescein (DCF) by mouse submandibular cells. 3′-O-(4-benzoyl)benzoyl adenosine 5′-triphosphate (BzATP), a P2X7 agonist, but not a muscarinic or an adrenergic agonist, reproduced the effect of ATP. The inhibition of phospholipase C by U73122 or the potentiation of P2X4 receptor activation with ivermectin did not modify the response to ATP. ATP did not increase the oxidation of DCFH in cells isolated from submandibular glands of P2X7 knockout mice or in cells pretreated with a P2X7 antagonist. The inhibition of protein kinase C or of mitogen-activated protein kinase (MAP kinase) or of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase blocked the oxidation of DCFH without affecting the increase of the intracellular concentration of calcium or the uptake of ethidium bromide in response to extracellular ATP. From these results it is concluded that the activation of the P2X7 receptors from submandibular glands triggers an intracellular signalling cascade involving protein kinase C and MAP kinase leading to the stimulation of NADPH oxidase and the subsequent generation of reactive oxygen species

Résistance du tissu adipeux épididymaire de souris OB/OB aux agents lipolytiques

Doctorat en sciences médicalesinfo:eu-repo/semantics/nonPublishe

Regulation by purinergic agonists of zinc uptake by rat submandibular glands.

The zinc uptake in rat submandibular cells was measured using fura2 as a fluorescent probe. Basal zinc uptake was observed in a 100 microM - 1 mM concentration range. Carbachol and isoproterenol had no effect but ATP4- dose-dependently increased the basal zinc uptake (half-maximal concentration: 250 microM). The purinergic agonist shifted the concentration curve for zinc to the left by one order of magnitude. The response to ATP was not reproduced by adenosine or ADP and was blocked by Coomassie blue. Calcium, nickel or lanthanum were inhibitors of zinc uptake, while the substitution of extracellular sodium by potassium or lithium increased the basal zinc uptake. We conclude that in submandibular cells zinc can permeate through the non-specific cation channel coupled to ATP-sensitive purinergic receptors.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Les aspects biochimiques de l'obésité.

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Etude de la lipolyse dans le tissu adipeux épididymaire de la souris ob/ob. -- Métabolisme

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ATP4- increases the intracellular calcium concentration in rat submandibular glands

1. The intracellular calcium concentration of a crude suspension from rat submandibular glands was increased by extracellular ATP. 2. The stimulatory effect of ATP was favored by removal of magnesium from the extracellular medium. ADP and adenosine had no effect. ATP did not modify the concentration of calcium in isolated rat pancreatic acini. 3. It is concluded that ATP is a potential neurotransmitter regulating the submandibular gland function. © 1993.In VitroJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Effet des agents purinergiques sur les mouvements d'ions dans les glandes sous-maxillaires.

Rat submandibular glands have been digested with collagenase P and a crude cellular suspension has been prepared. The [Ca2+]i and the pHi of these cells have been measured using fluorescent probes extracellular ATP increases the [Ca2+]i. At low concentrations ATP binds to a metabotropic receptor coupled to the mobilization of intracellular calcium stores. At high concentrations ATP activates a ionotropic receptor coupled to a non-specific cation channel permeant to calcium, sodium or zinc. The increase of the [Ca2+]i in response to ATP opens an anion permeability leading to a drop of the pHi. The acidification in response to ATP is potentiated by the removal of extracellular chloride or by the addition of an inhibitor of chloride channels in the incubation medium. Acetazolamide, an inhibitor of carbonic anhydrase blocks by 30% the intracellular acidosis in response to ATP. It is concluded that anions (among which bicarbonate is only a fraction) leave the cells by a chloride channel. The pHi does not decrease below 6.8 for two reasons: 1) the uptake of sodium by the non-specific cation channel and the ensuing depolarization on one hand and the decrease of the pHi on the other hand reverse the proton-moving force; 2) at low pHi the non-specific cation channel becomes permeable to protons. These results suggest that purinergic agonists are secretagogues. But at the opposite to classical secretagogues which increase the efflux of chloride, purinergic agonists rather increase the permeability to organic anions.English AbstractJournal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Un modèle de diabète expérimental, la souris db/db

SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe