title: Diadenosine polyphosphates regulate cytosolic calcium in human fibroblast cells by interaction with P2x purinoceptors coupled to phospholipase C.
abstract: The effects of diadenosine pentaphosphate (AP5A), and diadenosine hexaphosphate (AP6A) on the cytosolic-free Ca2+ concentration ([Ca2+]i) were evaluated in cultured human fibroblast cells (HF cells) using the fluorescent dye technique. AP5A, and AP6A concentration-dependently increased [Ca2+]i in HF cells. The addition of 10 mumol/1 AP5A and AP6A significantly increased [Ca2+]i in HF cells from 71 +/- 3 nmol/1 (n = 184) to 241 +/- 39 nmol/1 (n = 11; P < 0.001 compared to resting value) and to 227 +/- 26 nmol/1 (n = 23; P < 0.001), respectively. The purinoceptor P2 blockers, suramin and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), inhibited the diadenosine polyphophate-induced [Ca2+]i increase, whereas the P2y purinoceptor blocker, reactive blue, had no effect. Adenosinetriphosphate (ATP) and the P2x agonist, alpha 1 beta-methylene-ATP also significantly increased [Ca2+]i in HF cells, whereas the P2y agonist methylthio-ATP showed only a small [Ca2+]i response. Diadenosine polyphosphates mainly induced transplasmamembrane Ca2+ influx as was confirmed by experiments in the absence of extracellular Ca2+ or by manganese quenching studies. Organic (verapamil) and inorganic Ca2+ channel blockers (NiCI2) significantly reduced the AP6A induced transplasmamembrane Ca2+ influx. The inhibitor of phosphatidylcholine-specific phospholipase C, D609, significantly reduced the effect of diadenosine polyphosphates on [Ca2+]i in HF cells. It is concluded that diadenosine polyphosphates regulate transplasmamembrane Ca2+ influx after occupation of P2x receptors via activation of phosphatidylcholine-specific phospholipase C and hence of voltage-operated Ca2+ channels.
authors.affiliation: Medizinische Poliklinik, University of Münster, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Tepel
authors.forename: S
authors.initials: S
authors.lastname: Löwe
authors.forename: J R
authors.initials: JR
authors.lastname: Nofer
authors.forename: G
authors.initials: G
authors.lastname: Assmann
authors.forename: H
authors.initials: H
authors.lastname: Schlüter
authors.forename: W
authors.initials: W
authors.lastname: Zidek
mesh_terms: D001952:Bridged-Ring Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D015226:Dinucleoside Phosphates / Q000494:pharmacology*; D005347:Fibroblasts; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D008345:Manganese / Q000494:pharmacology; D009532:Nickel / Q000494:pharmacology; D009636:Norbornanes; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D058914:Purinergic Antagonists; D011983:Receptors, Purinergic / Q000378:metabolism*; D013498:Suramin / Q000494:pharmacology; D013805:Theobromine / Q000031:analogs & derivatives / Q000494:pharmacology; D013859:Thiocarbamates; D013871:Thiones / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
chemical_list: D001952:Bridged-Ring Compounds; D002121:Calcium Channel Blockers; D015226:Dinucleoside Phosphates; D009636:Norbornanes; D010726:Phosphodiesterase Inhibitors; D058914:Purinergic Antagonists; D011983:Receptors, Purinergic; D013859:Thiocarbamates; D013871:Thiones; D014662:Vasoconstrictor Agents; D014970:Xanthines; D008345:Manganese; C012275:P(1),P(5)-di(adenosine-5'-)pentaphosphate; C070070:diadenosine 5',5''''-P1,P6-hexaphosphate; C046498:tricyclodecane-9-yl-xanthogenate; C057837:3,7-dimethyl-1-propargylxanthine; D013498:Suramin; C022838:nickel chloride; D009532:Nickel; C051360:1,3-dipropyl-8-cyclopentylxanthine; D014700:Verapamil; D010738:Type C Phospholipases; D013805:Theobromine; D002118:Calcium; D016257:Fura-2