title: Extracellular ATP stimulates calcium influx in neuroblastoma x glioma hybrid NG108-15 cells.
abstract: ATP-induced changes in the intracellular Ca2+ concentration ([Ca2+]i) in neuroblastoma x glioma hybrid NG108-15 cells were studied. Using the fluorescent Ca2+ indicator fura-2, we have shown that the [Ca2+]i increased in response to ATP. ATP at 3 mM caused the greatest increased in [Ca2+]i, whereas at higher concentrations of ATP the response became smaller. Two nonhydrolyzable ATP analogues, adenosine 5'-thiotriphosphate and 5'-adenylyl-beta, gamma-imidodiphosphate, could not trigger significant [Ca2+]i change, but they could block the ATP effect. Other adenine nucleotides, including ADP, AMP, alpha beta-methylene-ATP, beta, gamma-methylene-ATP, and 2-methylthio-ATP, as well as UTP and adenosine, all had no effect on [Ca2+]i at 3 mM. In the absence of extracellular Ca2+, the effect of ATP was inhibited totally, but could be restored by the addition of Ca2+ to the cells. Upon removal of Mg2+, the maximum increase in [Ca2+]i induced by ATP was enhanced by about 42%. Ca(2+)-channel blockers partially inhibited the ATP-induced [Ca2+]i rise. The ATP-induced [Ca2+]i rise was not affected by thapsigargin pretreatment, though such pretreatment blocked bradykinin-induced [Ca2+]i rise completely. No heterologous desensitization of [Ca2+]i rise was observed between ATP and bradykinin. The magnitude of the [Ca2+]i rise induced by ATP increased between 1.5 and 3.1 times when external Na+ was replaced with Tris, N-methyl-D-glucamine, choline, or Li+. The addition of EGTA or verapamil to cells after their maximum response to ATP immediately lowered the [Ca2+]i to the basal level in Na(+)-containing or Na(+)-free Tris solution.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, R.O.C.
authors.forename: S H
authors.initials: SH
authors.lastname: Chueh
authors.forename: L S
authors.initials: LS
authors.lastname: Kao
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004305:Dose-Response Relationship, Drug; D016257:Fura-2; D005910:Glioma; D006822:Hybrid Cells / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D009447:Neuroblastoma; D009543:Nifedipine / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014700:Verapamil / Q000494:pharmacology; D020960:omega-Conotoxins
chemical_list: D002121:Calcium Channel Blockers; D010455:Peptides; D013729:Terpenes; D020960:omega-Conotoxins; C053423:Conus magus toxin; D000266:Adenylyl Imidodiphosphate; C022571:adenosine 5'-O-(3-thiotriphosphate); D019284:Thapsigargin; D000255:Adenosine Triphosphate; D014700:Verapamil; D000252:Calcium-Transporting ATPases; D009543:Nifedipine; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2