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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
4
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pubmed:dateCreated |
1996-9-18
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pubmed:abstractText |
The coupling between divalent cations and exocytosis of large dense-cored vesicles (LDCV) was studied with capacitance-detection techniques in nerve terminals of the rat neurohypophysis (NHP) and bovine chromaffin cells. Ba2+ substitution for Ca2+ produced kinetically distinct responses in the two preparations. In NHP terminals, Ba2+ ions behave as weak substitutes for Ca2+. Exocytotic events occur principally during depolarizing pulses, i.e., events are "stimulus-coupled" to Ba2+ entry through voltage-gated Ca2+ channels. Stimulus-coupled exocytosis apparently requires elevated submembrane cation concentrations that dissipate rapidly on hyperpolarization-induced Ca(2+)-channel closure. Intracellular dialysis of NHP terminals with Ba2+ does not evoke exocytosis, nor does it interfere with depolarization-evoked Ca2+ influx and exocytosis. In chromaffin cells, Ba2+ ions evoke a small quantity of stimulus-coupled secretion, but the dominant response is an additional pronounced poststimulus capacitance increase that outlasts channel closures by 20-50 sec. "Stimulus-decoupled" exocytosis is slow (approximately 25-40 fF/sec) compared with Ca(2+)-evoked stimulus-coupled exocytosis (approximately 1000 fF/sec). Decoupled secretion is not attributable to Ba2+ displacement of intracellular Ca2+ ions, because it is insensitive to 10 mM EGTA or thapsigargin. Slow exocytosis is initiated by inclusion of Ba2+ ions in the recording pipette and continues steadily for 5-12 min, producing a total increase of several thousand fF, which ultimately doubles or triples the original cell-surface area. We propose that two pathways of regulated exocytosis with distinct kinetics and divalent cation sensitivity exist in chromaffin cells. Only a single kinetic pattern is detected in NHP terminals, suggesting that mechanisms for secretion are not universally distributed in excitable cells.
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical | |
pubmed:status |
MEDLINE
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pubmed:month |
Feb
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pubmed:issn |
0270-6474
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
15
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pubmed:volume |
16
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
1370-9
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pubmed:dateRevised |
2007-11-14
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pubmed:meshHeading |
pubmed-meshheading:8778288-Animals,
pubmed-meshheading:8778288-Barium,
pubmed-meshheading:8778288-Calcium,
pubmed-meshheading:8778288-Cations,
pubmed-meshheading:8778288-Cattle,
pubmed-meshheading:8778288-Chromaffin System,
pubmed-meshheading:8778288-Exocytosis,
pubmed-meshheading:8778288-Kinetics,
pubmed-meshheading:8778288-Pituitary Gland, Posterior,
pubmed-meshheading:8778288-Time Factors
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pubmed:year |
1996
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pubmed:articleTitle |
Ba2+ ions evoke two kinetically distinct patterns of exocytosis in chromaffin cells, but not in neurohypophysial nerve terminals.
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pubmed:affiliation |
Department of Neurobiology and Anatomy, Medical College of Pennsylvania, Philadelphia 19129, USA.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
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