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Extracellular ATP Stimulates Calcium Influx in Neuroblastoma Glioma Hybrid NG108–15 Cells
Author(s) -
Chueh SheauHuei,
Kao LungSen
Publication year - 1993
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1993.tb09816.x
Subject(s) - thapsigargin , extracellular , chemistry , egta , adenosine , adenosine triphosphate , calcium , biophysics , intracellular , oligomycin , biochemistry , biology , atpase , enzyme , organic chemistry
— ATP‐induced changes in the intracellular Ca 2+ concentration ([Ca 2+ ] i ) in neuroblastoma glioma hybrid NG108–15 cells were studied. Using the fluorescent Ca 2+ indicator fura‐2, we have shown that the [Ca 2+ ] i increased in response to ATP. ATP at 3 m M caused the greatest increase in [Ca z+ ] i , whereas at higher concentrations of ATP the response became smaller. Two nonhydrolyzable ATP analogues, adenosine 5′‐thiotriphosphate and 5′‐adenylyl‐β, γ‐imidodiphosphate, could not trigger significant [Ca 2+ ] i change, but they could block the ATP effect. Other adenine nucleotides, including ADP, AMP, α,β‐methylene‐ATP, β,γ‐methylene‐ATP, and 2‐methylthio‐ATP, as well as UTP and adenosine, all had no effect on [Ca 2+ ] i at 3 m M. In the absence of extracellular Ca 2+ , the effect of ATP was inhibited totally, but could be restored by the addition of Ca 2+ to the cells. Upon removal of Mg 2+ , the maximum increase in [Ca 2+ ] i induced by ATP was enhanced by about 42%. Ca 2+ ‐channel blockers partially inhibited the ATP‐induced [Ca 2+ ] i rise. The ATP‐induced [Ca 2+ ] i rise was not affected by thapsigargin pretreatment, though such pretreatment blocked bradykinin‐induced [Ca 2+ ] i rise completely. No heterologous desensitization of [Ca 2+ ] i rise was observed between ATP and bradykinin. The magnitude of the [Ca 2+ ] 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 [Ca 2+ ] i to the basal level in Na + ‐containing or Na + ‐free Tris solution. Our results suggest that ATP stimulates Ca 2+ influx via at least two pathways: ion channels that are permeable to Ca 2+ and Na + , and pores formed by ATP 4‐ .