Ins(1,4,5)P3 formation and fluctuating chloride current response induced by external ATP in Xenopus oocytes injected with embryonic guinea pig brain mRNA.
In voltage-clamped Xenopus oocytes injected with embryonic guinea pig mRNA, effective concentrations of extracellular ATP elicited an inward fluctuating current. This current, carried by Cl-ions, was mainly dependent upon liberation of Ca2+ ions from stores as demonstrated by experiments using intracellular EGTA loading and TMB-8 superfusion. Neomycin inhibited these fluctuating currents indicating that the transplanted purinoceptor is linked to phospholipase C activity and triggers Ins(1,4,5)P3 formation. Ins(1,4,5)P3 production evoked by external ATP was clearly demonstrated by directly measuring the water-soluble Ins(1,4,5)P3 level in injected oocytes. Finally, it is suggested that the ATP effect was mediated by a Ca2+ release from Ins(1,4,5)P3 sensitive pools since heparin blocked the ATP responsiveness. The acquired purinoceptor may be made apparent to a P2 subtype since ATP and ADP were equipotent in eliciting Cl- current while AMP and Adenosine were ineffective in injected oocytes.
Fournier
F
F
UFR de Biologie, Université des Sciences et Techniques de Lille-Flandres-Artois, Villeneuve d'Asq, France.
Honoré
E
E
Collin
T
T
Guilbault
P
P
D000241:Adenosine / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000502:physiology; D002118:Calcium / Q000502:physiology; D002712:Chlorides / Q000502:physiology*; D004553:Electric Conductivity; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D008845:Microinjections; D012333:RNA, Messenger / Q000008:administration & dosage; D011983:Receptors, Purinergic / Q000502:physiology*; D014982:Xenopus laevis
D002712:Chlorides; D012333:RNA, Messenger; D011983:Receptors, Purinergic; D000249:Adenosine Monophosphate; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D000244:Adenosine Diphosphate; D005707:Gallic Acid; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D000241:Adenosine; D002118:Calcium