In many eukaryotic cell types, receptor activation leads to the formation of inositol 1,4,5-trisphosphate (IP3) which causes calcium ions (Ca) to be released from internal stores. Ca release was observed in response to the muscarinic agonist carbachol by fura-2 imaging of N1E-115 neuroblastoma cells. Ca release followed receptor activation after a latency of 0.4 to 20 s. Latency was not caused by Ca feedback on IP3 receptors, but rather by IP3 accumulation to a threshold for release. The dependence of latency on carbachol dose was fitted to a model in which IP3 synthesis and degradation compete, resulting in gradual accumulation to a threshold level at which Ca release becomes regenerative. This analysis gave degradation rate constants of IP3 in single cells ranging from 0 to 0.284 s-1 (0.058 +/- 0.067 s-1 SD, 53 cells) and a mean IP3 lifetime of 9.2 +/- 2.2 s. IP3 degradation was also measured directly with biochemical methods. This gave a half life of 9 +/- 2 s. The rate of IP3 degradation sets the time frame over which IP3 accumulations are integrated as input signals. IP3 levels are also filtered over time, and on average, large-amplitude oscillations in IP3 in these cells cannot occur with period < 10 s.
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January 01 1995
The lifetime of inositol 1,4,5-trisphosphate in single cells.
S S Wang,
S S Wang
Neurosciences Program, Stanford University, Pacific Grove, California 93950, USA.
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A A Alousi,
A A Alousi
Neurosciences Program, Stanford University, Pacific Grove, California 93950, USA.
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S H Thompson
S H Thompson
Neurosciences Program, Stanford University, Pacific Grove, California 93950, USA.
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S S Wang
Neurosciences Program, Stanford University, Pacific Grove, California 93950, USA.
A A Alousi
Neurosciences Program, Stanford University, Pacific Grove, California 93950, USA.
S H Thompson
Neurosciences Program, Stanford University, Pacific Grove, California 93950, USA.
Online ISSN: 1540-7748
Print ISSN: 0022-1295
J Gen Physiol (1995) 105 (1): 149–171.
Citation
S S Wang, A A Alousi, S H Thompson; The lifetime of inositol 1,4,5-trisphosphate in single cells.. J Gen Physiol 1 January 1995; 105 (1): 149–171. doi: https://doi.org/10.1085/jgp.105.1.149
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