Diadenosine polyphosphates regulate cytosolic calcium in human fibroblast cells by interaction with P2x purinoceptors coupled to phospholipase C.
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.
Tepel
M
M
Medizinische Poliklinik, University of Münster, Germany.
Löwe
S
S
Nofer
J R
JR
Assmann
G
G
Schlüter
H
H
Zidek
W
W
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
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