title: Observations of calcium dynamics in cortical secretory vesicles.
abstract: Calcium (Ca(2+)) dynamics were evaluated in fluorescently labeled sea urchin secretory vesicles using confocal microscopy. 71% of the vesicles examined exhibited one or more transient increases in the fluorescence signal that was damped in time. The detection of transient increases in signal was dependent upon the affinity of the fluorescence indicator; the free Ca(2+) concentration in the secretory vesicles was estimated to be in the range of ∼10 to 100 μM. Non-linear stochastic analysis revealed the presence of extra variance in the Ca(2+) dependent fluorescence signal. This noise process increased linearly with the amplitude of the Ca(2+) signal. Both the magnitude and spatial properties of this noise process were dependent upon the activity of vesicle p-type (Ca(v)2.1) Ca(2+) channels. Blocking the p-type Ca(2+) channels with ω-agatoxin decreased signal variance, and altered the spatial noise pattern within the vesicle. These fluorescence signal properties are consistent with vesicle Ca(2+) dynamics and not simply due to obvious physical properties such as gross movement artifacts or pH driven changes in Ca(2+) indicator fluorescence. The results suggest that the free Ca(2+) content of cortical secretory vesicles is dynamic; this property may modulate the exocytotic fusion process.
authors: Department of Physiology and the Bernard Katz Minerva Centre for Cell Biophysics, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors: Adi
authors: A
authors: Raveh
authors: Michael
authors: M
authors: Valitsky
authors: Liora
authors: L
authors: Shani
authors: Jens R
authors: JR
authors: Coorssen
authors: Paul S
authors: PS
authors: Blank
authors: Joshua
authors: J
authors: Zimmerberg
authors: Rami
authors: R
authors: Rahamimoff
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000737:chemistry / Q000494:pharmacology; D020865:Calcium Channels, P-Type / Q000737:chemistry / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology; D005456:Fluorescent Dyes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D047331:Lytechinus / Q000378:metabolism; D018613:Microscopy, Confocal; D016012:Poisson Distribution; D022142:Secretory Vesicles / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D047269:Strongylocentrotus / Q000378:metabolism; D014966:Xanthenes / Q000737:chemistry
chemical_list: D000814:Aniline Compounds; D002121:Calcium Channel Blockers; D020865:Calcium Channels, P-Type; C409648:Fluo 4; D005456:Fluorescent Dyes; D014966:Xanthenes; D002118:Calcium