Agonist modulation of intracellular calcium oscillations in tracheal smooth muscle cells

G. G. Sieck, Y. S. Prakash, M. S. Kannan

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!n freshly dissociated porcine trachéal smooth muscle (TSM) cells loaded with fluo-3, the dynamics of intraceliular Ca2+ ([Ca2+]i) responses to ACh and endothelin-I (ET-I) were examined using a real-time confocal microscope. ACh (10 nM-IO μM) induced [Ca2+]i oscillations that did not vary in amplitude and persisted in the absence of extracellular Ca2+. Oscillation frequency, but not amplitude, depended on ACh concentration, increasing - 3 fold across the ACh range. Oscillation frequency also slowed during the course of exposure to a given ACh concentration, suggesting muscarinic receptor desensitization. The rise (0.4 to 2 s) and fall (I to 4 s) times of each [Ca], wave did not vary with ACh concentration, but wave velocity increased. ET-1 ( 10 nM-1 u,M) also induced [Ca], oscillations of comparable amplitudes to ACh. However, unlike ACh, oscillation frequency and wave velocity were not dependent on ET-1 concentration. The relatively constant amplitude of [Ca2]i waves in response to varying concentrations of both ACh and ET-1 suggests an all-or-none event at the level of SR Cu4 release in TSM cells. It is likely that control of oscillation frequency and wave velocity are major factors in ACh regulation of [Ca '], but not ET-1. Variations in [Ca], exposure time could play an important role in regulating smooth muscle contractions or other Ca2-dependent processes. Supported by N!H grant HI,51736 and by fellowships from Abbott Laboratories.

Original languageEnglish (US)
Pages (from-to)A660
JournalFASEB Journal
Issue number3
StatePublished - Dec 1 1996

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics


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