Purine and pyrimidine nucleotide-sensitive phosphoinositidase C in ampulla from frog semicircular canal.
A microassay was developed to screen the abilities of ATP analogues to stimulate phosphoinositidase C in single ventral regions (including dark cells and sensory cells) of ampullas microdissected from posterior vertical semicircular canals of Rana ridibundo and labeled with myo-[3H]inositol. ATP induced a dose-dependent and saturable increase of total [3H]linositol phosphate production accompanied by an equivalent decrease in the [3H]phosphoinositide pool. The rank order of analogues revealing agonistic potencies for phosphoinositidase C activation was as follows: uridine 5'-triphosphate > or = adenosine 5'-O-[3-thiophosphate] tetralithium > adenosine 5'-O-[2-thiodiphosphate] trilithium > or = ATP > or = ADP = inosine 5'-triphosphate > or = guanosine 5'-triphosphate > or = 2-methylthio-adenosine 5'-triphosphate tetrasodium > or = 2'-desoxy-thymidine 5'-triphosphate > or = cytidine 5'-triphosphate = (alpha, beta)-methyl ATP > AMP, whereas adenosine 3',5'-cyclic monophosphate and adenosine were almost devoid of activity. For antagonists, 1,4'-diisothiocyanostilbene-2, 2'-disulfonic acid was far more active than suramin for competitive inhibition of ATP-induced enzyme stimulation, whereas reactive blue 2 acted as a noncompetitive inhibitor. Results indicate that the putative P2 receptors triggering phosphoinositidase C activation in ventral ampullary epithelium from frog semicircular canal exhibit mainly the functional properties of P2Y and P2U receptors.
Butlen
D
D
Institut National de la Santé et de la Recherche Médicale Unité 426, Département de Physiologie, Faculté de Médecine Xavier Bichat, Paris, France.
Bernard
C
C
Ammar
A
A
Ferrary
E
E
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D004210:Dissection; D004789:Enzyme Activation; D005260:Female; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000096:biosynthesis; D008297:Male; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D011685:Purine Nucleotides / Q000494:pharmacology*; D058913:Purinergic Agonists; D011742:Pyrimidine Nucleotides / Q000494:pharmacology*; D011895:Rana ridibunda; D011983:Receptors, Purinergic / Q000378:metabolism / Q000502:physiology; D012665:Semicircular Canals / Q000201:enzymology*; D013498:Suramin / Q000494:pharmacology
D007295:Inositol Phosphates; D011685:Purine Nucleotides; D058913:Purinergic Agonists; D011742:Pyrimidine Nucleotides; D011983:Receptors, Purinergic; D013498:Suramin; D000255:Adenosine Triphosphate; D010727:Phosphoric Diester Hydrolases; C021491:glycerophosphoinositol glycerophosphodiesterase; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid