Cytosolic calcium facilitates release of secretory products after exocytotic vesicle fusion

  • Fernández-Chacón R
  • de Toledo G
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We monitored single vesicle exocytosis by simultaneous measurements of cell membrane capacitance as an indicator of fusion and amperometric detection of serotonin release. We show here that vesicle-plasma membrane fusion in rat mast cell granules is followed by a variable, exponentially distributed, delay before bulk release. This delay reflects the time required for the expansion of the exocytotic fusion pore, lasting, on average, 231 ms in resting cytosolic calcium, [Ca2+]i(50 nM). In the presence of [Ca2+]iin the low micromollar range, the lag between fusion and release was reduced to 123 ms. The characteristics of the amperometric signals were unchanged by [Ca2+]i. These results show a novel site of regulation in the exocytotic process, the fusion pore, which may represent a different mechanism facilitating transmitter release. © 1995.

Author-supplied keywords

  • Amperometry
  • Cell capacitance
  • Exocytosis
  • Transmitter release

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