The lifetime of inositol 1,4,5-trisphosphate in single cells

Samuel S.H. Wang, Adawia A. Alousi, Stuart H. Thompson

Research output: Contribution to journalArticle

93 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)149-171
Number of pages23
JournalJournal of General Physiology
Volume105
Issue number1
DOIs
StatePublished - Jan 1 1995

All Science Journal Classification (ASJC) codes

  • Physiology

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