Purine and pyrimidine nucleotide-sensitive phospholipase A(2) in ampulla from frog semicircular canal.
This study was attempted to characterize pharmacologically the P2Y receptors triggering phospholipase A(2) (PLA(2)) activation in ampulla from frog semicircular canal. A microassay was developed to screen the abilities of UTP analogs to stimulate [(3)H]arachidonic acid release by labeled ampullas. At 26 degrees C UTP induced a dose-dependent and saturable increase of PLA(2) activity (apparent activation constant 1.3 +/- 0.4 microM, Hill coefficient 0.9 +/- 0.2, maximal stimulating factor 2.0 +/- 0.1). The rank order of potency of agonists for PLA(2) activation was UTP > or = UDP > adenosine 5'-O-(2-thiodiphosphate) = adenosine 5'-O-(3-thiotriphosphate) > or = ATP = 2-methylthio-ATP > or = ADP = diadenosine tetraphosphate > or = alpha,beta-methylene-ATP = CTP > 2' and 3'-O-(4-benzoylbenzoyl)-ATP > or = AMP = UMP >> uridine and adenosine. UTP- and 2-methylthio-ATP-induced PLA(2) activations were inhibited by U-73122, GF-109203X, and methyl arachidonyl fluorophosphate. Basal activity was stimulated by phorbol ester and epinephrine and reduced by vasotocin, isoproterenol, prostaglandin E(2), cAMP, and forskolin. H-89 restored the cAMP- and forskolin-inhibited PLA(2) activities. Results indicate that P2Y receptor-mediated PLA(2) stimulation requires phopholipase C and protein kinase C activations and basal activity is inhibited by agonist-stimulated cAMP-dependent mechanisms.
Teixeira
M
M
Institut National de la Santé et de la Recherche Médicale, Unité 426, Faculté de Médecine Xavier Bichat, 75870 Paris Cedex 18, France.
Bernard
C
C
Ferrary
E
E
Butlen
D
D
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D007700:Kinetics; D008301:Maleimides / Q000494:pharmacology; D008954:Models, Biological; D010741:Phospholipases A / Q000378:metabolism*; D011685:Purine Nucleotides / Q000494:pharmacology*; D011742:Pyrimidine Nucleotides / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology; D011895:Rana ridibunda; D020239:Receptor Cross-Talk; D018048:Receptors, Purinergic P2 / Q000502:physiology; D012665:Semicircular Canals / Q000201:enzymology / Q000502:physiology*; D013449:Sulfonamides; D013498:Suramin / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology
D004791:Enzyme Inhibitors; D004963:Estrenes; D007211:Indoles; D007546:Isoquinolines; D008301:Maleimides; D011685:Purine Nucleotides; D011742:Pyrimidine Nucleotides; D011760:Pyrrolidinones; D018048:Receptors, Purinergic P2; D013449:Sulfonamides; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D016718:Arachidonic Acid; D013498:Suramin; D000255:Adenosine Triphosphate; D010741:Phospholipases A; C070515:bisindolylmaleimide I; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D014544:Uridine Triphosphate