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Related Experiment Videos

Do caged-Ca2+ compounds mimic the physiological stimulus for secretion?

A F Oberhauser1, I M Robinson, J M Fernandez

  • 1Department of Physiology and Biophysics, Mayo Clinic, Rochester, MN 55905, USA.

Journal of Physiology, Paris
|January 1, 1995
PubMed
Summary
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Flash photolysis of caged calcium (Ca2+) in mast and chromaffin cells causes an artifactual capacitive response, unlike GTP gamma S stimulation. This indicates Ca2+ triggers non-secretory events, differing from physiological stimulation.

Area of Science:

  • Cell biology
  • Neuroscience
  • Biochemistry

Background:

  • Exocytosis is a fundamental cellular process involving vesicle fusion with the plasma membrane.
  • Calcium (Ca2+) and GTP gamma S are key triggers for exocytosis in various cell types.
  • Mast cells and chromaffin cells are widely studied models for exocytotic mechanisms.

Purpose of the Study:

  • To investigate the precise sequence of events during Ca2+- or GTP gamma S-induced exocytosis.
  • To differentiate between capacitive changes and actual vesicle fusion events.
  • To assess the physiological relevance of rapid, global Ca2+ increases versus localized Ca2+ influx.

Main Methods:

  • Flash photolysis of caged Ca2+ and GTP gamma S to induce rapid, global stimulation.
  • Measurement of exocytosis using cell membrane capacitance and amperometry.

Related Experiment Videos

  • Pulsed-laser imaging to study localized Ca2+ influx under physiological conditions.

    • Main Results:

    • Ca2+ triggered an immediate capacitance increase, but amperometric spikes were delayed, suggesting non-secretory events.
    • GTP gamma S triggered a simultaneous capacitance increase and secretion, without discrepancy.
    • Localized Ca2+ influx during physiological stimulation contrasts with the global Ca2+ stimulus artifact.

    Conclusions:

    • A rapid, global Ca2+ increase can induce artifactual capacitive responses not linked to vesicle fusion.
    • Capacitance measurements alone may not accurately reflect exocytosis under non-physiological stimulation.
    • Localized Ca2+ signaling is crucial for physiological exocytosis, unlike global stimulation methods.