Kinetics of Ca2+ release evoked by photolysis of caged InsP3 in rat submandibular cells

T. Takeo, S. Suga, J. Wu, Y. Dobashi, T. Kanno, M. Wakui

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Quantitative time-resolved measurements of cytosolic Ca2+ release by photolysis of caged InsP3 have been made in single rat submandibular cells using patch clamp whole-cell recording to measure the Ca2+-activated Cl- and K+ currents. Photolytic release of InsP3 from caged InsP3, at 100 Joules caused transient inward (V(H) = 60 mV)) and outward (V(H) = 0 mV)) currents, which were nearly symmetric in their time course. The inward current was reduced when pipette Cl- concentration was decreased, and the outward current was suppressed by K+ channel blockers, indicating that they were carried by Cl- and K+, respectively. Intracellular pre-loading of the InsP3 receptor antagonist heparin or the Ca2+ chelator EGTA clearly prevented both inward and outward currents, indicating that activation of Ca2+-dependent Cl- and K+ currents underlies the inward and the outward currents. At low flash intensities, InsP3 caused Ca2+ release which normally activated the K+ and Cl- currents in a mono-transient manner. At higher intensities, however, InsP3 induced an additional delayed outward K+ current ((K(delay)). I(K(delay)) was independent of the initial K+ current, independent of extracellular Ca2+, inhibited by TEA, and gradually prolongated by repeated flashes. The photolytic release of Ca2+ from caged Ca2+ did not mimic the I(K(delay)). It is suggested that Ca2+ releases from the InsP3-sensitive pools in an InsP3 concentration-dependent manner. Low concentrations of InsP3 induce the transient Ca2+-dependent Cl- and K+ currents, which reflects the local Ca2+ release, whereas high concentrations of InsP3 induce a delayed Ca2+-dependent K+ current, which may reflect the Ca2+ wave propagation.

Original languageEnglish (US)
Pages (from-to)387-397
Number of pages11
JournalJournal of Cellular Physiology
Issue number3
StatePublished - Mar 1998
Externally publishedYes

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Cell Biology


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