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Intracellular Calcium Pools in Neuroblastoma × Glioma Hybrid NG108–15 Cells
Author(s) -
Chueh SheauHuei,
Liu JinAnn,
Kao LungSen
Publication year - 1990
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.1471-4159.1990.tb03136.x
Subject(s) - gtp' , calcium , chemistry , guanosine , biophysics , guanosine triphosphate , inositol , intracellular , calcium in biology , biochemistry , biology , receptor , enzyme , organic chemistry
The intracellular nonmitochondrial calcium pools of saponin‐permeabilized NG108–15 cells were characterized using inositol 1,4,5‐trisphosphate (IP 3 ) and GTP. IP 3 or GTP alone induced release of 47 and 68%, respectively, of the calcium that was releasable by A23187. GTP induced release of a further 24% of the calcium after IP 3 treatment, whereas IP 3 induced release of a further 11 % of the calcium after GTP treatment. Guanosine 5′‐ O ‐(3‐thio)triphosphate had little effect on IP 3 ‐induced calcium release but completely inhibited GTP‐induced calcium release. In contrast, heparin inhibited the action of IP 3 but not that of GTP. The results imply the existence of at least three nonmitochondrial pools: (a) 31% is releasable by IP 3 and GTP, (b) 11% is releasable by IP 3 alone, and (c) 24% is releasable by GTP alone. GTP enhanced calcium uptake in the presence of oxalate with an EC 50 of 0.6 μ M and stimulated calcium release in the absence of oxalate with an EC 50 of 0.32 μ M . The similar EC 50 values for these dual effects of GTP on calcium movement suggest that GTP exerts its dual action by the same mechanism.