title: Temporally resolved, independent stages of individual exocytotic secretion events.
abstract: The stages of the complex events involved in exocytotic secretion after vesicle-cell membrane fusion have been examined at the level of individual vesicles. Catecholamine flux from single bovine adrenal medullary cells was measured with carbon-fiber microelectrodes firmly touching the cell surface. The data reveal that secretion during exocytotic events has three distinct stages: a small increase in catecholamine flux, a rapid, but not instantaneous, rise to a maximum, followed by an exponential decrease in the flux. These stages are interpreted in the following ways. The initial stage corresponds to catecholamine secretion through a fusion pore. The rate of pore expansion appears to control the rise time of the flux to its maximum value. The final exponential stage is consistent with chemical dissociation of the intravesicular matrix or gel.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill 27599-3290, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Schroeder
authors.forename: R
authors.initials: R
authors.lastname: Borges
authors.forename: J M
authors.initials: JM
authors.lastname: Finnegan
authors.forename: K
authors.initials: K
authors.lastname: Pihel
authors.forename: C
authors.initials: C
authors.lastname: Amatore
authors.forename: R M
authors.initials: RM
authors.lastname: Wightman
mesh_terms: D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D055592:Biophysical Phenomena; D001703:Biophysics; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008561:Membrane Fusion / Q000502:physiology; D008839:Microelectrodes; D008954:Models, Biological; D009994:Osmolar Concentration; D012996:Solutions
chemical_list: D002395:Catecholamines; D012996:Solutions; D001464:Barium