title: Cytosolic calcium facilitates release of secretory products after exocytotic vesicle fusion.
abstract: 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+]i in 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.
authors.affiliation: Departamento de Fisiologiá Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Fernández-Chacón
authors.forename: G
authors.initials: G
authors.lastname: Alvarez de Toledo
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D015550:Cell Degranulation; D003600:Cytosol / Q000502:physiology; D005089:Exocytosis; D008407:Mast Cells / Q000502:physiology*; D008561:Membrane Fusion; D008564:Membrane Potentials; D051379:Mice; D008817:Mice, Mutant Strains; D018408:Patch-Clamp Techniques; D051381:Rats; D012701:Serotonin / Q000378:metabolism
chemical_list: D012701:Serotonin; D002118:Calcium